External Hard Drive - Does it Need To Spin Down? Is "Safely Remove" Enough?

[johnsmoke]

So I recently bought a 2 TB WD My Passport drive to use with my Ubuntu (14.04) machine. I plan on formatting to ext4 as well as encrypting with TrueCrypt. Anyway, I plugged it in just to see if Ubuntu would recognize it, and it did... spun right up, mounted etc... Now I went to properly remove the drive by right clicking it in the dashboard, and it unmounts it (drive disappears from launcher on left). However, still hear the drive spinning and there is still power to the drive.... My question is - does the drive need to completely spin down/power off prior to removing it? Or does a "safely remove" suffice? Another big reason that I ask is because once I encrypt the drive and format to ext4, I know that ext4 is a tad more sensitive to dismounting properly, and could cause corruption of data if not ejected/dismounted properly.

[grahammechanical]

Does the OS give you a message that the drive can now be safely removed or something like that?

Before disconnecting devices, you must unmount them first. This is similar to "Safely Remove" in Windows in that the device won't unmount until data is finished being written to the device, or until other programs are finished using it. This applies to all types of storage devices, including flash drives, flash cards, external hard drives, ipods and other media players, and even remote storage like Samba or NFS shares.

Failure to unmount before disconnecting the device can result in loss of data and/or a corrupted file system. There are no exceptions to this rule. Be safe - unmount your drives before disconnecting them!

https://help.ubuntu.com/community/Mount/USB

I would guess that unmounting does not switch off power to the device. Just as plugging the device in brings power to the device so unplugging it would remove power. In the mean time the drive's platters will still be spining. Otherwise, powering down would slow down data transfer if the device need to power up before it could be written to.

Regards,

[slickymaster]

You can safely unmount and spin-down an external hard disk from the terminal most easily by using the command-line functionality of udisks

udisks --unmount /dev/sdb# <- '#' being the drive in question

Then to safely remove (i.e. spindown- you will hear it click and spin-down), use only sdb, for example:

udisks --detach /dev/sdb

It is of crucial importance here that you use sdb or sdc without a partition number when using the detach option; i.e. sdb1 or sdc1 will not work. The partition must be unmounted first and then the disk itself spun down.

See https://help.ubuntu.com/community/Au...ountPartitions for reference.

[johnsmoke]

Thanks for the replies. So just clicking "safely remove" isn't sufficient? A spin down is definitely necessary to ensure data is not corrupted? I read that most drives now "auto park" the heads when powering down anyway... I just want to be sure that I properly remove the drive, unmount etc. prior to removing the USB cable and disconnecting from my system.

[Mark Phelps]

I've found that the USB interface makes the difference in that, when I unmount a USB 3 drive, it powers off; but when I unmount a USB 2 drive, it does not. In the latter case, I turn it off and wait until it stops spinning before I move it.

[ajgreeny]

I've found that the USB interface makes the difference in that, when I unmount a USB 3 drive, it powers off; but when I unmount a USB 2 drive, it does not. In the latter case, I turn it off and wait until it stops spinning before I move it.

Turn off what?

If you have a portable, USB powered disk you have the choice only to turn off the computer OS which is hardly convenient.

[Mark Phelps]

Turn off what?

The external USB cases that I have with my disks have a power switch on the front. I am able to turn them off that way.

[johnsmoke]

So should you spin the drive down and power it off before unplugging? My drive is usb powered - when I "safely remove" it looks like it unmounts (disappears from the launcher on the left side) - but the drive is still on and the disk is still spinning.... Is there any way that I can properly power this down prior to unplugging from the machine? I just want to be sure I do this correctly so that my data does not get corrupted.

[Dennis N]

If it is powered from the USB port, I just eject or safely remove the drive and then unplug the USB cable. So far (several years) no data has ever been lost.

There is the hdparm utility which has a command option to make a drive spin down to standby. You have to try and see if your drive responds. In the terminal, read man hdparm for information.

[johnsmoke]

So what is the general consensus on the USB-powered drives? Is doing a "safely remove" sufficient enough to be able to pull the cord even though the drive is still spinning? I'm willing to do that if it's safe... I just don't want to load up this drive with tons of stuff, then mess it up by not ejecting it properly.

Dennis, thanks for the info on hdparm... I'm a bit confused by it though. Seems like you can set intervals for the spin down... maybe those settings are saved for good for the drive... not sure if a one time immediate spin down is possible... or if needed based on my above comments.