Howto help USB boot drives

[sudodus]

Content of the posts

1. A tool that helps boot some computers from [other] USB boot drives - Chainloader - (This first post, no link needed)

2. Check download and clone image in Windows

3. Chainloading with the 40_custom method when you have linux and grub installed

4-5. Add a pendrive to grub simply by inserting the pendrive and doing 'sudo update-grub'

6. Pendrive speed test

7. Pendrive ability to boot

8. Pendrive lifetime

9. Repair the partition table and file system of a pendrive

13. Checking the iso file and the boot drive - detailed tips

14. Restore a USB boot drive

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A tool that helps boot some computers from [other] USB boot drives - Chainloader

What is new, why this tutorial, when I have already written Howto make USB boot drives? Isn't it enough to be able to use mkusb or the other tools?

It can be hard to boot some computers with some USB pendrives. New and fast USB 3 pendrives are nice when booted, but can be unwilling to boot from the built in menu of some computers. This is described at the following links

https://help.ubuntu.com/community/In...#Prerequisites
https://help.ubuntu.com/community/In...puter_from_USB

I have found, that

- the same USB pendrive can boot with one operating system, but not another one, in some computers, while it boots happily in other computers with almost any operating system,

- the Ubuntu 13.04 based grub2 bootloader is 'a good booter' in many computers (it is used in the original One Button Installer),

- many USB pendrives boot when selected from the grub menu, even if they will not boot from the built in menu of some computers.

So I made a small chainloader, that

- is willing to boot and

- is able to chainload to other pendrives or other mass storage devices.

When this chainloader is installed into a pendrive, that is good for booting (but maybe slow), we have a tool to help [other] USB boot drives.

Comparison with Plop

Maybe you have used or heard of Plop, a tool to boot from one device (typically a CD or floppy drive) and help booting another drive, typically a USB drive. That tool is useful for old computers. The chainloader is useful for middle-aged computers, for example computers without a CD/DVD drive, where it can be hard to boot from a USB drive, and when you want to run from a fast USB 3 drive that is unwilling to boot.

UEFI

New computers are often delivered with another operating system that is locked into UEFI, which makes things complicated. This chainloader is not running in UEFI mode. Use other tools and methods, for example according to the following links

https://help.ubuntu.com/community/UEFI
https://help.ubuntu.com/community/UEFIBooting
https://help.ubuntu.com/community/Boot-Repair


Pendrives that are good for booting

The following pendrives were tested by Pendrivelinux a few years ago. At least some of them are still available in the market (and I do not mean the second hand market)

SanDisk – Cruzer Micro 128M-2G
RIDATA – Ritek Mini Spin 128M-2G
OCZ – Rally2 (Old Style) 128M-2G
OCZ – Mini Kart 128M-1-2G
PQI – PQI i810 1-2G
PNY – Attache 1-2G

I have SanDisk – Cruzer Micro 4 GB and 16 GB, and they are also good booters.

I have SanDisk – Cruzer Blade 4 GB (I bought a 10-pack). They are good booters and quite cheap (at least in Sweden) and I can recommend them for the chainloader.

USB 3 pendrives

The Kingston DataTraveler Ultimate G2 16GB USB 3 pendrive is tested and recommended as a good booter by http://usb.userbenchmark.com/ but it can be hard to find in the market today.

I have Sandisk Extreme USB 3.0 16GB and 32GB and they are very fast and give good value for the money. I have also a Transcend JetFlash 700 USB 3.0 32GB. It is not very fast compared to Sandisk Extreme but definitely faster than standard USB 2 pendrives and a good booter, that I have tested for a long time. I use it for the One Button Installer; there is space enough for many tarballs. Sandisk Cruzer Blade 4 GB is cheap and slow, and a reliable booter, that has only failed once for me during years.

Tests of speed and ability to boot are described in posts #6 and #7 (in this thread).

The Chainloader software

A compressed image file of the chainloader software is available at the following links

http://phillw.net/isos/linux-tools/
https://drive.google.com/folderview?...jA&usp=sharing

-rw-r--r-- 1 root root 24426712 dec 31 23:41 chainloader-101MB_13.04.img.xz

The corresponding md5sum is

8d41e2873511e08c05a1ddc3c061d230  chainloader-101MB_13.04.img.xz

and it can be installed with the following command (if mkusb is in the same directory)

sudo bash mkusb chainloader-101MB_13.04.img.xz

mkusb helps you write to the correct target device (your pendrive). The chainloader expands from 24MB to 101MB. You can use a small pendrive (if it is a good booter).

The file grub.cfg looks like this (and you can modify it if you wish)

set timeout=20
set default=1

#echo listing available drives (hdX) and partitions (hdX,msdosY) 
#ls
#echo -n "Press ESC to continue to the menu "
#sleep -v -i ${timeout}

menuentry "Boot (chainload) first drive (on hd0) usually internal, maybe not now" {
        insmod part_msdos
        insmod fat
        set root='(hd0)'
        chainloader +1
}
menuentry "Boot (chainload) drive (on hd1)" {
        insmod part_msdos
        insmod fat
        set root='(hd1)'
        drivemap -s (hd0) ${root}
        chainloader +1
}
menuentry "Boot (chainload) drive (on hd2)" {
        insmod part_msdos
        insmod fat
        set root='(hd2)'
        drivemap -s (hd0) ${root}
        chainloader +1
}
menuentry "Boot (chainload) drive (on hd3)" {
        insmod part_msdos
        insmod fat
        set root='(hd3)'
        drivemap -s (hd0) ${root}
        chainloader +1
}
menuentry "Boot (chainload) drive (on hd4), edit if necessary: set root='(hd5)' ..." {
        insmod part_msdos
        insmod fat
        set root='(hd4)'
        drivemap -s (hd0) ${root}
        chainloader +1
}
menuentry "List available drives (hdX) and partitions (hdX,Y)" {
    ls
    echo -n "Press ESC to continue to the menu "
    sleep -v -i 20
}
menuentry "Long list drives (hdX) and partitions (hdX,Y)" {
    ls -l
    echo -n "Press ESC to continue to the menu "
    sleep -v -i 20
}
menuentry "Long list drive 1 (hd1) and partition 1 (hd1,1), edit if necessary" {
    ls -l (hd1,1)
    echo -n "Press ESC to continue to the menu "
    sleep -v -i 20
}

Chainloading with the 40_custom method when you have linux and grub installed

In the particular case, that you have linux and grub installed there is also the 40_custom method, and it is better than using a USB chainloader. As already described, some pendrives boot from grub even if they won't boot from the computer's own (bios/uefi) USB boot menu entry. See the a detailed description in post #3.

[sudodus]

Check download and clone image in Windows

First download the chainloader and md5sums.txt from this link(1) or link(2).

Then download the following help programs

http://www.md5summer.org
http://www.7-zip.org
http://sourceforge.net/projects/win32diskimager

Check that the download was successful with md5summer according to the file md5sums.txt.

Next extract the image file with 7-zip

from chainloader-101MB_13.04.img.xz to chainloader-101MB_13.04.img

Then prepare to write the extracted image file (without the ending xz) with win32diskimager according to the picture. Win32diskimager looks for img files. Don't mind that the picture is borrowed from another project and contains another file name.

WARNING: Double-check that the target device is the correct one (in the window of win32diskimager) before you start writing! Otherwise you might overwrite and destroy important data.



Using win32diskimager is described with screenshots in the following link https://wiki.ubuntu.com/Win32DiskImager/iso2usb

[sudodus]

Chainloading with the 40_custom method when you have linux and grub installed

In the particular case, that you have linux and grub installed there is also the 40_custom method, and it is better than using a USB chainloader. As already described, some pendrives boot from grub even if they won't boot from the computer's own (bios/uefi) USB boot menu entry. See the following link for a background about grub Scripts: /etc/grub.d/

Edit the file

sudo nano /etc/grub.d/40_custom

Add the following text to the file 40_custom (notice that it is important to keep the first lines, that come with the file)

menuentry "External drive (on hd1) if no eSATA drive connected. edit if necessary" {
        insmod part_msdos
        insmod fat
        set root='(hd1)'
        drivemap -s (hd0) ${root}
        chainloader +1
}

and run the command

sudo update-grub

Then you will get a grub menu option to boot from a second drive (hd1), which could be a USB pendrive. If another drive is hd1, you can edit the line to (hd2) etc.
If there is no grub menu, press the left shift key during boot, and it should appear.

[C.S.Cameron]

The truly lazy should be able to add a pendrive to grub, without going to 40_custom, simply by inserting the pendrive and doing:

sudo update-grub

[sudodus]

Yes, I agree that it is a very convenient method, and should be enough in many cases, but I think it will be specific for that particular pendrive and its current operating system.

[sudodus]

Pendrive speed test

I made this speed test because I make installers that use cloning with dd and expansion of compressed tarballs. So the test measures the speed of those particular operations. See also the general speed tests at this link to USB 3.0 Flash Drive Speed Tests

The focus of this test was on 8 GB drives, because I make 8 GB images for the One Button Installer, but there are also some 4, 16, 32 GB pendrives, that I know after years of usage.

When using USB pendrives, you often notice that they are slow compared to internal disks. There are big differences between fast and slow pendrives, and it makes a big difference, when you use them as general mass storage devices, but the difference seems to be even bigger, when you boot an operating system, that is installed in the pendrive.

USB 3 is much faster than USB 2. The flash hardware is often limiting the read and write speed below the limits of the USB system. USB 3 pendrives are often but not always made with faster hardware than standard USB 2 pendrives. This makes it worthwhile to use USB 3 pendrives in USB 2 ports, so USB drives can be useful also with old computers without USB 3.

Reading and writing single or few big files can be fairly fast with USB pendrives, but the time to start and stop writing is often much longer in pendrives compared to hard disk drives and SSDs. It makes many pendrives very slow when writing many small files, like when you install an operating system or backup a file system or directory tree. This is why I included a test expanding a tarball with many small files. It is actually installing the text version of the One Button Installer, writing 68417 files with the total data amount 1.2 GB. The average file size is 17.7 kB (10-base). The complete result of the test is shown in attached files, and includes reading and writing single big files with dd.

Write small files MB/s
in USB 2 port

18.989    SanDisk Extreme (scsi) / new 32 GB
17.855    SanDisk Extreme (scsi) / new 16 GB - undersized
 5.224    Kanguru SS3 (scsi) / 16 GB - undersized
 4.673    SanDisk Extreme (scsi) / old 32 GB - damaged
 3.797    Kanguru FlashBlu (scsi) / 8GB USB 2, write-protect switch
 3.313    JetFlash Transcend 32GB (scsi) / 'new 700' good booter - undersized
 2.953    JetFlash Transcend 16GB (scsi) / 'old 700' USB 3 – undersized
 2.769    JetFlash Transcend 4GB (scsi) / old with green rim
 2.731    Kingston DT Ultimate G3 (scsi) / 32GB USB 3 - undersized
 2.629    SanDisk Ultra (scsi) / 8 GB USB 2
 2.561    Kingston DataTraveler 3.0 (scsi) / 100 G3 8GB - undersized
 2.446    SanDisk Cruzer Blade (scsi) / 4 GB, USB 2, good booter
 2.257    JetFlash Transcend 8GB (scsi) / 760 USB 3 - undersized
 2.091    JetFlash Transcend 8GB (scsi) - 500 USB 2
 1.923    UFD 2.0 Silicon-Power8G (scsi) / Ultima U01
 1.680    Verbatim STORE N GO (scsi) / 8GB - undersized
 1.427    Corsair Voyager (scsi) / 8GB USB 2 'Flash Voyager'
 1.294    Kingston DataTraveler 2.0 (scsi) / 101 G2 8GB - undersized

in USB 3 port

32.333    TOSHIBA External USB 3.0 (scsi) / HDD 320 GB
23.926    SanDisk Extreme (scsi) / 16 GB - undersized 15693664256 bytes
23.006    SanDisk Extreme (scsi) / 32 GB
 8.365    Kanguru SS3 (scsi) / 16 GB - undersized
 4.747    JetFlash Transcend 32GB (scsi) / 'new 700' good booter - undersized 31608274944 bytes
 4.069    Kanguru FlashBlu (scsi) / 8GB USB 2, write protect switch
 3.987    Kingston DT Ultimate G3 (scsi) / 32GB USB3 - undersized 31440502784 bytes
 2.795    JetFlash Transcend 16GB (scsi) / 'old 700' USB 3 - undersized 15812526080 bytes
 2.658    Kingston DataTraveler 3.0 (scsi) / 100 G3 8GB undersized 7803174912 bytes
 2.583    JetFlash Transcend 8GB (scsi) / 760 USB 3 -undersized 7902068736 bytes
 2.187    SanDisk Cruzer Blade (scsi) / 4GB, USB 2, good booter

Read 2 GB file with random content (cloning with dd) MB/s
in USB 2 port

36.1    SanDisk Extreme (scsi) / old 32 GB, damaged works only in USB 2
36.1    SanDisk Extreme (scsi) / new 32 GB
36      JetFlash Transcend 16GB (scsi) / 'old 700' USB 3 – undersized
36      SanDisk Extreme (scsi) / new 16 GB - undersized
35.9    Kingston DataTraveler 3.0 (scsi) / 100 G3 8GB - undersized
35.9    JetFlash Transcend 32GB (scsi) / 'new 700' good booter - undersized
35.3    Kanguru SS3 (scsi) / 16 GB - undersized
32.8    Kingston DT Ultimate G3 (scsi) / 32GB USB 3 - undersized
30.4    JetFlash Transcend 8GB (scsi) / 760 USB 3 - undersized
29.2    Kanguru FlashBlu (scsi) / 8GB USB 2, write-protect switch
22.2    SanDisk Cruzer Blade (scsi) / 4 GB, USB 2, good booter
21.9    SanDisk Ultra (scsi) / 8 GB USB 2
21.3    JetFlash Transcend 8GB (scsi) - 500 USB 2
20.5    Kingston DataTraveler 2.0 (scsi) / 101 G2 8GB - undersized
20.2    Corsair Voyager (scsi) / 8GB USB 2 'Flash Voyager'
17.9    Verbatim STORE N GO (scsi) / 8GB - undersized
15.1    UFD 2.0 Silicon-Power8G (scsi) / Ultima U01
14.9    JetFlash Transcend 4GB (scsi) / old with green rim

in USB 3 port

104      SanDisk Extreme (scsi) / 16 GB - undersized 15693664256 bytes
 74.6    Kanguru SS3 (scsi) / 16 GB - undersized
 64.1    TOSHIBA External USB 3.0 (scsi) / HDD 320 GB
 60.1    JetFlash Transcend 32GB (scsi) / 'new 700' good booter - undersized 31608274944 bytes
 59      Kingston DT Ultimate G3 (scsi) / 32GB USB3 - undersized 31440502784 bytes
 51.6    JetFlash Transcend 16GB (scsi) / 'old 700' USB 3 - undersized 15812526080 bytes
 49.3    JetFlash Transcend 8GB (scsi) / 760 USB 3 -undersized 7902068736 bytes
 38.9    Kingston DataTraveler 3.0 (scsi) / 100 G3 8GB undersized 7803174912 bytes
 37.8    SanDisk Extreme (scsi) / 32 GB
 28.7    Kanguru FlashBlu (scsi) / 8GB USB 2, write protect switch
 20.3    SanDisk Cruzer Blade (scsi) / 4GB, USB 2, good booter

Write 2 GB file with random content (cloning with dd) MB/s
in USB 2 port

29.5    SanDisk Extreme (scsi) / new 32 GB
27.5    SanDisk Extreme (scsi) / new 16 GB - undersized
26.9    SanDisk Extreme (scsi) / old 32 GB default (finished with tar)
20.9    JetFlash Transcend 16GB (scsi) / 'old 700' USB 3 – undersized
17.4    Kingston DT Ultimate G3 (scsi) / 32GB USB 3 - undersized
16.9    SanDisk Extreme (scsi) / old 32 GB full test finished with dd
16.3    Kanguru SS3 (scsi) / 16 GB - undersized
13.9    JetFlash Transcend 32GB (scsi) / 'new 700' good booter - undersized
10.9    Kanguru FlashBlu (scsi) / 8GB USB 2, write-protect switch
 7.8    SanDisk Ultra (scsi) / 8 GB USB 2
 7.2    JetFlash Transcend 4GB (scsi) / old with green rim
 7.1    UFD 2.0 Silicon-Power8G (scsi) / Ultima U01
 5.9    JetFlash Transcend 8GB (scsi) / 760 USB 3 - undersized
 5.9    JetFlash Transcend 8GB (scsi) - 500 USB 2
 5.1    Kingston DataTraveler 3.0 (scsi) / 100 G3 8GB - undersized
 4.9    Corsair Voyager (scsi) / 8GB USB 2 'Flash Voyager'
 4.7    SanDisk Cruzer Blade (scsi) / 4 GB, USB 2, good booter
 4.1    Verbatim STORE N GO (scsi) / 8GB - undersized
 3.2    Kingston DataTraveler 2.0 (scsi) / 101 G2 8GB - undersized

in USB 3 port

88      TOSHIBA External USB 3.0 (scsi) / HDD 320 GB
44.1    SanDisk Extreme (scsi) / 16 GB - undersized 15693664256 bytes
43.6    SanDisk Extreme (scsi) / 32 GB
30.0    Kanguru SS3 (scsi) / 16 GB - undersized
25.9    Kingston DT Ultimate G3 (scsi) / 32GB USB3 - undersized 31440502784 bytes
20.8    JetFlash Transcend 16GB (scsi) / 'old 700' USB 3 - undersized 15812526080 bytes
20.5    JetFlash Transcend 32GB (scsi) / 'new 700' good booter - undersized 31608274944 bytes
10.5    Kanguru FlashBlu (scsi) / 8GB USB 2, write protect switch
 5.7    JetFlash Transcend 8GB (scsi) / 760 USB 3 -undersized 7902068736 bytes
 5.4    Kingston DataTraveler 3.0 (scsi) / 100 G3 8GB undersized 7803174912 bytes
 4.7    SanDisk Cruzer Blade (scsi) / 4GB, USB 2, good booter

Comments

Sandisk Extreme is much faster (approximately 3 times faster than the second best, Kanguru SS3, and 5 times faster than the third best, Jetflash Transcend 700) writing 'many small files' compared to the other tested pendrives, but not as fast as a USB 3 HDD. Kanguru FlashBlu was fastest writing 'many small files' among the 8 GB pendrives, even though it is a USB 2 device and competed with some USB 3 devices.

There are several pendrives that read single big files with high speed, so if that is what you need, there are many good candidates. Writing speed of single big files differs more than reading, but the results are more even than writing 'many small files', and the ranking is somewhat different. See also the attached files.

Disclaimer

This is a fairly simple speed test without statistical validation. The pendrives were bought as a regular consumer from a web store, and in most cases a single specimen of each model was tested. Make your own test, if you need reliable results for your particular application.

-o-

Edit: There was a request from the Lubuntu mailing lists to upload the scripts and input files to perform this test (or a similar one), so they are uploaded now. See this link

http://phillw.net/isos/linux-tools/usb-speed-test/

[sudodus]

Pendrive ability to boot

If you want to use a USB pendrive to boot computers, it is important that it is a good booter. Most pendrives (that are not damaged) can boot most computers, but some of them have problems. The USB hardware and firmware on the motherboard might have problems with the pendrive. You can say that some pendrives do not cooperate with some computers.

I made this bootability test because I make installers and help programs and script for installers. The focus of this test was on 8 GB drives, because I make 8 GB images for the One ButtonInstaller, but there are also some 4, 16, 32 GB pendrives, that I know after years of usage.

Booting from a computer's built in boot menu

This is a survey of the ability to boot from a computer's built in boot menu. Several pendrives were tested in some different computers. It is far from a complete or statistically validated test, but I hope it can help to select a pendrive when it is important to boot from it. At least it will show some aspects that you should consider before deciding what to buy.

It may be possible to boot via the Chainloader, even if the computer cannot boot the pendrive and it's system from the built in boot menu.

0. The pendrives are listed in alphabetical order.

The focus was on 8 GB drives, because I make 8 GB images for the One ButtonInstaller, but there are also some 4, 16, 32 GB pendrives, that I know after years of usage.

Corsair Flash Voyager 8 GB, USB 2
Kanguru Flashblu2 8GB, USB 2
Kingston DT 100 G3 USB 3, 8 GB
Kingston DT 101 G2 USB 2, 8 GB
Kingston DT Ultimate G3 USB 3, 32 GB
Sandisk Cruzer Blade USB 2, 4 GB
Sandisk Cruzer Ultra USB 2, 8 GB
Sandisk Extreme (USB 3), 16, 32 GB
Transcend Jetflash 500 USB 2, 8 GB
Transcend Jetflash 700 USB 3, 16, 32 GB
Transcend Jetflash 760 USB 3, 8 GB
Verbatim Micro 8 GB, USB 2

1. All tested pendrives can boot the following computers

Toshiba Satellite Pro C850, Toshiba Satellite Pro A300, Asus (motherboard) M2N-VM DVI, Dell Dimension 4600, IBM Thinkpad T42

2. HP Elitebook 8560p boot problems - typical of 'middle-aged to newer' HP professional class laptops

With an exception for an 'old 32 GB' Sandisk Extreme (USB3), all pendrives booted in a similar way (but at very different speed). Booting from cloned iso files and Unetbootin systems works. Booting from grub2 works with the version of grub that comes with Ubuntu 14.04 LTS, when the boot flag is added to the partition.

The following comment might explain why I have considered Sandisk Extreme a poor booter:

- A Sandisk Extreme 'old 32 GB' (USB3) can boot the chainloader but not the built in OBI. This pendrive works well in most situations in USB 2 ports, but after an (electronic?) damage, it is extremely slow in USB 3 ports. This pendrive has 'always' been a poor booter, even before the damage. Maybe it was a bad specimen from the beginning. Newer Sandisk Extreme pendrives show as good booting ability as Transcend 700.

3. IBM Thinkpad T42 boot problems

Corsair Flash Voyager 8GB USB 2 seemed to work (the LED was flashing) but it never finished the booting (after 'Loading initial ramdisk ...'). After 'hard reset' and cold boot (power off and waiting a minute) it booted correctly.

Transcend Jetflash 500 8GB USB 2 was not recognized by the BIOS, so it could not be selected. It failed several times. It was recognized by the BIOS when connected via a USB hub, and then it could boot.

The other pendrives work properly (but of course, this IBM has a Pentium M CPU, so it cannot boot iso files with PAE kernels). See this link

https://help.ubuntu.com/community/Lubuntu-fake-PAE

4. Compaq Presario 5640 boot problems

This computer is very old, has a Pentium II CPU with 400 MHz and 192 MB RAM. It can boot from USB via Plop, but there are problems with some USB pendrives and systems on them.

The following pendrives can boot the 'OBI version 2.2 text' based on Ubuntu mini-iso 13.10. I used nomodeset to get it running. There are some error outputs, but nevertheless booting continues and succeeds with most of the tested pendrives.

Corsair Flash Voyager 8 GB, USB 2
Kanguru Flashblu2 8GB, USB 2
Kingston DT 100 G3 USB 3, 8 GB
Kingston DT Ultimate G3 USB 3, 32 GB
Sandisk Extreme 'new 32 GB' (USB 3)
Transcend Jetflash 500 USB 2, 8 GB
Transcend Jetflash 700 USB 3, 16 GB
Transcend Jetflash 760 USB 3, 8 GB
Verbatim Micro 8 GB, USB 2

The following pendrives do not work because they are not found after the Plop bootloader transfers control to the USB system.

Kingston DT 101 G2 USB 2, 8 GB
Sandisk Cruzer Blade USB 2, 4 GB (which has worked 'everywhere' before)
Sandisk Cruzer Ultra USB 2, 8 GB

The OBI version 2.2 booted via the USB chainloader did not work. Probably chainloading twice {Plop - USB chainloader - final system} will lose track of some important data.

Test of extra pendrives (for this very old computer)

A Transcend Jetflash 520S 32 GB, USB 2 'very small pendrive with metal casing' boots with Xubuntu Precise installed. An old Sandisk Cruzer Micro 4GB with Ubuntu Boot Repair could boot too. An old Sandisk Cruzer Micro 16 GB with OBI version 2.1 based on Lubuntu 13.10 booted, but the system did not want to run properly. The pendrive itself worked.

Comments

Most pendrives in this test are good booters. Some of them fail to boot some computer. The computers are very different in age and type, but it is hard to draw any definite conclusions about computers not tested as well as pendrives not tested. You should also notice, that in some cases the operating system (at least the bootloader) makes a difference. This was the case with the HP laptop.

So get a fast pendrive unless the price is too high! You can also choose between one fast USB 3 pendrive and use it as a temporary device (flash the iso file, image file or data set when you need it), or several standard USB 2 pendrives, which you dedicate to different systems or data sets. I can buy ten Sandisk Cruzer Blades (4GB) for about the same price as two Sandisk Extreme 16 GB or one Sandisk Extreme 32 GB. Jetflash Transcend 700 and Kingston DT Ultimate G3 USB 3, 32 GB, are also good choices, somewhat cheaper and slower than Sandisk Extreme.

Disclaimer

This is a fairly simple boot test without statistical validation. The pendrives were bought as a regular consumer from a web store, and in most cases a single specimen of each model was tested. Make your own test, if you need reliable results for your particular application. You should also notice that this test does not evaluate the lifetime or sensitivity to damage of the pendrives.

[sudodus]

Pendrive lifetime

Memory cards and USB pendrives have the same kind of hardware inside, so this post is relevant to memory cards too.

USB pendrives have a rather bad reputation concerning lifetime, but there is evidence that they have improved, and can last quite long nowadays, at least when managed in a good way.

"The reports of my death have been greatly exaggerated."
Markus B Twain

Summing the information up a couple of years ago:If you don’t physically ruin your drive, you have about 1,500 connections and about 10,000 write cycles for each memory cell before you can expect the USB pendrive or flash card to fail. This is typical for MLC flash memory cells. SLC flash memory lasts ten times longer and is used in solid state drives (SSD) and it seems also in some expensive pendrives. Probably the average has improved now, but we can expect differences depending on the manufacturing process.

The market is changing. Search the internet for pendrive slc. I found that the 'MX-ES Series USB3.0 pendrive' utilizes SLC NAND according to the manufacturer, and also 'Winkom USB-3.0 Pendrive SLC DDR flash'. Recently (in 2015) I found a USB 3 pendrive with built-in trim and S.M.A.R.T commands. It is still way too expensive, but soon such pendrives will probably be common and cheap. See this link.

When old pendrives get slower (typically reduce the writing speed to half), I wipe the whole device with mkusb (overwrite with zeros). That way I have recovered the original (or near original) write speed. I think it is a way to relieve the internal management of the memory cells (connecting logical cells with physical cells, maybe by releasing cells that have been written to seldom because they have been storing data). But don't do it too often, because of the wear.

When a pendrive or memory card is read-only

• On some pendrives and on many memory cards there is a small mechanical switch for write protection, that can toggle between read/write and read-only. You might have set it read-only without intention.
• Reboot the computer and try again to wipe the first megabyte with mkusb.
• Disconnect other USB devices. Sometimes USB devices can disturb the function for each other.
• Try other USB ports and another computer.
• Try another operating system (Windows, MacOS) in another computer.
• If you still cannot wipe the first megabyte of the drive, and the drive is read-only, it is 'gridlocked', and the next stage is that it will be completely 'bricked'.

Repair methods are described in the next post, #9, Repair the partition table and file system of a pendrive

-o-

This link to a post by DuckHook in the Ubuntu Forums describes how a flash drive works, and how it can fail, first getting read-only 'gridlocked', then totally 'bricked'.

The following link describes different hardware problems and what can be done to repair a USB stick/pendrive/flash drive http://www.wikihow.com/Repair-a-USB-Flash-Drive. Look for the tips and warnings!

The next link describes in detail how flash memory works and wears.

http://www.storage-switzerland.com/a...st_Longer.html

Apparently writing to a vfat drive with this "sync" option can ruin it. The following link is ten years old, but who knows if it can still work like that.

http://readlist.com/lists/vger.kerne...22/111748.html

The following links are shorter, but may add some information

http://www.flashbay.co.uk/blog/usb-life-expectancy

http://www.zdnet.com/article/usb-dri...ct-or-fiction/

http://www.dallasnews.com/business/t...lash-drive.ece

http://getusb.info/what-is-the-life-...sb-flash-drive

[sudodus]

Repair the partition table and file system of a pendrive

Restore the original speed

When old pendrives get slower (typically reduce the writing speed to half), I wipe the whole device with mkusb (overwrite with zeros). That way I have recovered the original (or near original) write speed. I think it is a way to relieve the internal management of the memory cells (connecting logical cells with physical cells, maybe by releasing cells that have been written to seldom because they have been storing data). But don't do it too often, because of the wear.

Repair file systems

Often when a pendrive does not work, it is not bricked, but the file system or partition table is damaged. This can be repaired with the same kind of tools as are used for hard disk drives.

Repair Windows file systems (FAT and NTFS) with Windows tools

chkdsk /f X:

or if you suspect bad sectors,

chkdsk /r X:

where X: is the drive letter (volume letter) for the target partition as seen from Windows.

Another problem of Windows file systems is fragmentation. After a while they might need defragmentation. But it means a lot of writing, and I would suggest a method that creates less writing on the pendrive:

- Copy the content of the pendrive to another drive, backup. Do not clone, instead you should copy the directory structure with the files.
- Format the drive alias create a new file system (or, only if it has become very slow, wipe the whole device).
- Restore alias copy back the content from the backup.

If you have no Windows system and cannot borrow a Windows computer you can try to repair a FAT file system with dosfsck, that comes with the package dosfstools,

sudo apt-get install dosfstools

sudo dosfsck -a /dev/sdxy

where x is the drive letter and y is the partition number, for example /dev/sdb1 for the first partition in drive b. See

man dosfsck

for more details.

Sometimes this 'least destructive method' of the option -a is not enough, and you need the option -r to 'interactively repair the filesystem'.

sudo dosfsck -r /dev/sdxy

This -r option was necessary when I had provoked a damaged file system by unplugging while a big iso file was copied (to a pendrive with a FAT32 file system).

Repair linux file systems with linux tools

sudo e2fsck -f /dev/sdxy

or if you suspect bad blocks

sudo e2fsck -cfk /dev/sdxy

where x is the drive letter and y is the partition number, for example /dev/sdb1 for the first partition in drive b. See

man e2fsck

for more details.

Advanced repair of a partition table, file system and/or recovery of files

If you still have problems, you can use other methods for repair or recovery of the files, that are more powerful but also more risky. If the data are valuable it is a very good idea to make a cloned copy to a card or pendrive of at least the same size, and try to repair the file system and/or recover files from the cloned copy.

Particularly if you suspect bad sectors (a hardware damage on the drive), it is a good idea to clone with ddrescue.

Install ddrescue

sudo apt-get install gddrescue

learn about it at the info page

info ddrescue

and follow one of the examples.

Otherwise (no bad sectors), it might be a good idea to clone with mkusb-dus, because it is safer, 'wraps a safety belt around dd'.

dus /dev/sdx

where x is the drive letter of the source drive (and you use a menu to select the target drive (to become the cloned copy).

Notice that you should not use Clonezilla in these cases, because you want to clone also parts of the drive which might not be marked as containing file data. (Otherwise Clonezilla is a good tool.)

Testdisk and PhotoRec

Learn how to get and how to use testdisk and photorec from the instructions at https://www.cgsecurity.org/

If you need more detailed help, you are welcome to start an own thread here at the Ubuntu Forums, for example in the hardware or general help subforums.

Refresh the partition table and file system(s) - the wipe menu in mkusb

When a USB drive is recognized as a mass storage device, /dev/sdx, by for example

sudo lsblk -fm

the following method can often make a failing drive available to use again, even if the file system could not be repaired. Wipe means that the previous partition table and file systems will be overwritten with zeros, so do not expect to recover data afterwards.

Wipe [only] the first megabyte to prepare for a fresh partition table without any remaining and confusing data with mkusb according to this link. If you wish you can make a partition table and file system too from the wipe menu. Afterwards you can use gparted to create or modify a partition table with partitions and file systems. See the attached screenshot files. mkusb version 12 alias mkusb-dus is easier to use than the previous versions of mkusb.

If it is not possible to wipe the first megabyte of the drive, and the drive is read-only, it is 'gridlocked', and the next stage is that it will be completely 'bricked'. See Post #8. Pendrive lifetime

Attempts to repair the pendrive's hardware

The following link describes different hardware problems and what can be done to repair a USB stick/pendrive/flash drive http://www.wikihow.com/Repair-a-USB-Flash-Drive. Look for the tips and warnings!

[QDR06VV9]

This as you have already pointed out

The following pendrives do not work because they are not found after the Plop bootloader transfers control to the USB system.
Sandisk Cruzer Blade USB 2, 4 GB (which has worked 'everywhere' before)
Sandisk Cruzer Ultra USB 2, 8 GB

Is the only problems I have encountered..
What else do need me to test sudodus??
Kind Regards