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Thread: Ubuntu 12.04 won't see raid 0

  1. #51
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    Re: Ubuntu 12.04 won't see raid 0

    OK I got it working and i couldn't have done it without you two guys... A BIG HUG ALL AROUND!! ok maybe thats a little too pink

    Anyways.. THANKS!!

    For other posters and desperate people

    You need to make a "reservered for bios" partition on EVERY disk
    You need to make a boot partition - you make that by creating a EXT partition and mount it as boot.
    You need to turn off the HP raid controller in the bios by switching to Sata. I went with legacy sata but there is another sata option that might work..

    Just one more question..

    In regards to the required boot partition:

    I have 4 disk SD a b c d - currently i have installed the boot partition on SDA. Now if that disk dies (SDA) i have a raid5 and so would survive it but i assume my system would still crash because SDA was the disc with my boot partition - is this correct? and if yes how should i circumvent it? create a boot partition on all discs?

  2. #52
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    Re: Ubuntu 12.04 won't see raid 0

    Did you create the partition and used it as /boot or you only created it so you can put the boot flag on it?

    If you used it as /boot that was a wrong decision. Yes, if sda dies it will not boot even though raid5 can work without one disk. But ubuntu can't work without /boot.

    What you should have done is make the identical partition on all disks and make a raid1 md device from all four partitions (yes, you can make raid1 with four partitions) and use it as /boot. In that case the same files will be on all four disks and it will work without any one of them. But not without two disks since that is raid5 limitation and your / will still be raid5.
    Darko.
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    Ubuntu 12.04 LTS 64bit & Windows 7 Ultimate 64bit

  3. #53
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    Re: Ubuntu 12.04 won't see raid 0

    I think I found something in their doc's last night. It said the B120 does not have it's own processor, so uses the system processors for RAID. Doing that, I'm starting to think that controller uses an Intel ICHx chipset, which is considered as fakeRAID. Looking at the MS Server 2008 manuals on that server and that controller... If you set the BIOS: SATA mode to AHCI on an HP server with that controller, it's going to ask for an additional driver... In other doc's it said that if set to AHCI, then it sees a ICHx chipset and if not it loads a more generic type controller driver.

    It also said somewhere else:
    NOTE: When the SAS-enabled riser board with the Smart Array B320i controller is installed in the server, the embedded Smart Array
    B120i controller is automatically disabled. In the absence of another storage controller or an expander backplane, front drives operate
    in AHCI or Legacy mode. In these two modes, the drives are not part of a hardware RAID or a member of a logical drive. The Locate,
    Drive status, and Do not remove LEDs in the drive carrier are disabled.
    Since you are not installing another RAID card, you have to turn it off and put it into those modes manually. So, here's something to try to get around that.

    his gets into this area:
    With some motherboards (rare), using AHCI may be a problem when using Ubuntu. If it works properly with AHCI, keep this mode because it provides enhanced performances, but if it doesn't, switch to IDE mode (normally more compatible). Don't forget that your motherboard has two different SATA controllers, so you have to configure the one handling the SATA port where your hard disk drive is connected. Look at "PCH SATA Control Mode" and/or "GSATA3 Ctrl Mode" options in "Integrated Peripherals" section of your BIOS. Don't hesitate to test AHCI mode if the controller is already set up in IDE mode. If your hard disk drive is connected to the GSATA3 controller from Marvell, you may also try to connect it on a port handled by the Intel PCH controller.
    Go into the system system BIOS. Go to where you set the embedded SATA controller options. The note on that is going to say something like "Enable Dynamic Smart Array Controller B120i"... At that option there should be 2 or 3 modes:
    This option will be there:
    - Enable Dynamic HP Smart Array B120i RAID Support
    You do NOT want to select this...

    The other option or options will be:
    - Enable SATA Legacy Support
    This next option may or may not be there:
    - Enable SATA AHCI Support (HP Tech says this option was removed for some newer servers... so may not be there)

    So it looks like you need first try AHCI enabled, If it doesn't then try SATA legacy.

    Going by what the SUSE install docs say for that server, unfortunately, this may affect "how" it is installed and the hdd type drivers Linux installs/loads when it installs. So changing that mode in BIOS may affect how an installed system acts. As I saw "somewhere" in your server's Linux doc's for that controller, that option needed to be set before the Linux install process. (I think that was in the SUSE install doc's, when using mdadm.)

    Hope that info helps...

    EDIT--- I see you found that on your own while I was writing this....
    Last edited by MAFoElffen; March 22nd, 2013 at 09:16 PM.
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  4. #54
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    Re: Ubuntu 12.04 won't see raid 0

    Additional to darko... and reading back through...

    How many partitions are you using for RAID5? I remember you saying you had 4 3TB disks and you were going 3+1 spare.

    I may be wrong. (Sort of like saying, I'm no doctor, but...) Wouldn't it make more sense to go with smaller partitions (for example 7+1), so that when you it's assembled you end up with more storage and with a smaller spare. That way you aren't losing so much space? 1/4 of your total storage seems a bit for a spare... And would take forever to rebuild, right?

    In RAID5 you use about 25% for parity. So with the 3+1 at 3x3TB, you are at around 6.75TB usuable. With 7+1, you end up with 7.85TB usable, with a 100% faster rebuild time.

    Sorry- Just thinking out loud.

    On the boot issue, I'm thinking that you did several things at once... And just changing the SATA mode might have enabled the boot to work. So it may boot into a RAID5 with that option set in BIOS now. I have to agree with Darko, whichever way, if set to a boot to/on only one disk, if that disk goes down, it's dead. If still not working to RAID5, then mirror it so you have a backup avenue.
    Last edited by MAFoElffen; March 22nd, 2013 at 09:44 PM.
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  5. #55
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    Re: Ubuntu 12.04 won't see raid 0

    How would you make the 8 partitions? Instead of 4, you make 2 partitions on each disk? Wouldn't that put way too much pressure on the disk since instead of writing "once" it actually writes "twice" on different physical sectors at the same time on each disk.

    I wouldn't really do that. I haven't gone into too much investigating, but it looks like the disks will be closer to failure like that.

    I don't recall any more if one disk was planned for spare, I thought all 4 will be part of raid5 without spares. Hence the 9TB device shown in few partitioning images before. 3 x 3TB usable + 3TB parity.
    Darko.
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  6. #56
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    Re: Ubuntu 12.04 won't see raid 0

    You're right of course on possible performance issues, but not in practice.. My mind wanders today because no sleep last night. (I just finished converting IBM ServeRAID Manager for 12.04lts and newer, packaging it debian and installing it on my IBM Xseries Server... Now works great through shh on current Ubuntu!)

    Hard to write in two places on the same disk at one time. If it were HardRAID, that is not possible. On Software RAID it is possible to have multiple partitions on same disk and have one raid array with even just one physical disk. I do it all the time with mdadm in virtual for server dev testing... And:
    Quote Originally Posted by kragen View Post
    Linux software raid is more flexible than hardware raid or true raid because rather than forming a raid arrays between identical disks, the raid arrays are created between identical partitions. As far as I understand, if you are using hardware raid between (for example) two disks, then you can either create a raid 1 array between those disks, or a raid 0 array. Using software raid however, you could create two sets of identical partitions on the disks, and for a raid 0 array between two of those partitions, and a raid 1 array between the other two. If you wanted to you could probably even create a raid array between two partitions on the same disk! (not that you would want to!)

    The process of setting up the a raid array is simple:

    1. Create two identical partitions
    2. Tell the software what the name of the new raid array is going to be, what partitions we are going to use, and what type of array we are creating (raid 0, raid 1, etc...)
    mdadm manages the caching between the the partitions... But since striping between physical disks is faster... You are right in that it may turn out slower.
    Last edited by MAFoElffen; March 23rd, 2013 at 01:11 AM.
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  7. #57
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    Re: Ubuntu 12.04 won't see raid 0

    Mike, another important thing that I didn't think of last night. You will create a raid5 from 8 partitions instead of 4, right?

    But raid5 tolerates only one member failure to keep working and if any physical disk fails you lose two members since you have 2 partitions on each disk that are members of the array. If any disk fails the array will fail which is no raid at all.

    Unless you are talking about two separate raid5 arrays of 4 partitions each, but that's a different matter, and in that case you still dedicate 2 partitions to parity (one for each array), not 7+1 in your example above.

    The quote in your last post talks about flexibility that you can have 2 partitions on two disks each, and make one raid0 and one raid1 arrays which is more flexible than HW raid. I agree with that, but not with all partitions on the same disk to be membes of the same array. Different arrays, yes. Otherwise it's not much protection against failure.
    Darko.
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  8. #58
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    Re: Ubuntu 12.04 won't see raid 0

    LOL! Statistical probability...

    Always remember: "RAID Is Not Backup."

    It would scare you, but there is more likelihood of a failure from an URE read /write error on large data stores than a total physical drive failure. The likihood of encountering a URE is once every 11.3TB's. In a 3TB disk, that's 1 in 4 total disk (full) reads. In a running RAID, this is not a problem as it reads, sees the URE, goes to other redundant parts of the RAID, reads good data, goes on as it rewrites to the sector where the URE occurred, that it read from. The probability varies when there is a failure and it has to rebuild, hence the Big Read... Talking about a good read:
    http://www.standalone-sysadmin.com/b...praise-raid-5/

    I feel safer when I find those bad sectors and can mark them out, than some large storage where I haven't found them "yet."

    But since we are talking software RAID, you are not constrained to technology within a hardware bios...You can migrate to RAID50, RAID6 or RAID60 without having to buy another controller. With RAID6 you can have 2 members fail and run...

    Even with LVM... I run LVM with virtual guest hosts, you can run LVM with created synced backup pseudo parity. Backup LVM partitions track individual incremental changes from the time/point of creation.

    Back-to.... is was concern on large (3TB) members being more likely to have a failure than a total physical disk failure.... But then again, people do it all the time, right?
    Last edited by MAFoElffen; March 23rd, 2013 at 07:23 PM.
    Multi-Boot= Various flavours of Windows, Linux and Unix... Ubuntu user # 33563, Linux user # 533637
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  9. #59
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    Re: Ubuntu 12.04 won't see raid 0

    Hey Darko

    I will make the boot as you mention - Thanks..

    In regards to the ways i could make the RAIDS...

    I really appriciate the info and it is certainly something to think about in the furthur but for now i keep think i will keep my Raid5 design as it is cause i really need to get past this and get on with the IDS projekt

    But thanks again guys.. you did good allround..

    Mike check my pm

  10. #60
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    Re: Ubuntu 12.04 won't see raid 0

    Hi,

    To get RAID5 working on internal controller you need to purchase 512 Mb FBWC memory module to it.
    But the internal controller is not fast in Windows 2012 or Redhat compared to a software Raid with Ubuntu 13.04 when turning the controller to a SATA AHCI mode and use Software RAID. Software RAID in ubuntu is 20-30 Mb/s faster for read and writing 5-7 Mb/s when using 6 disks as RAID5 in test with Windows 2012, Redhat and Ubuntu.
    Only issue is that I have only got the server to boot and working correctöy with Ubuntu kernel 3.8.0.19. All other newer kernels gives kernel panics after a while or won't boot at all.

    But now when VMWare has released Hypervisor 5.5 that is working fine now with this platform I will make all installations using Hypervisor 5.5 instead of Ubuntu Server with VMWare Workstation as Hypervisor 5.0 and 5.1 did not work correctly on HP DL/ML 3*0e models that was the reason to start using Ubuntu on this platform..

    Just my 5 cents.

    KR
    /M

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