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Thursday, June 16, 2005

Adaptec RAID (Linux)

IBM x-series servers are shipped with Adaptec HostRAID, that supports RAID 0/1/10. It turns out that this "RAID" is regular AIC-7902B U320 SCSI controller, and RAID functionality is provided in driver (=software RAID!), i.e. you can use aic79xx driver and see all of hard disk separately, no matter how you've configured your "RAID" using Adaptec BIOS utility.

And here comes the fun part - If you want use your disks as RAID, you have two options:
  1. Use general linux md driver - this looks like preffered solution, since I do not know how good that proprietary Adaptec driver (see below) is tested.
  2. Use mystical a320raid driver "provided" by Adaptec. This driver is published under 'adaptec' license, i.e. its not OpenSource driver. Moreover, Adaptec does not publicly provide this driver for 2.6.x. kernels even in binary form. As far as I saw, SUSE SLES 9 and Mandrake provide this driver for 2.6.x kernels, but they can not be freely downloaded (and no src.rpm as well).
The bottom line is - HostRAID RAID solution announced on IBM x-series server (and surely many others) is a software RAID solution, unless you install additional hardware in special slot (IBM ServerRAID-7k I think)
Some links on the subject:
SUSE discussion
Mandrake rpm page

Have sweet nightmares...

posted by Hai Zaar at Thursday, June 16, 2005

9 Comments:

  • 1. IBM Server Guide CD uses kernel 2.4.x to access the RAID. It utilizes drivers released by Adaptec for 2.4.x kernels. As of Jul 2005 IBM support had nothing positive to tell on the subject.

    2. You can mount driver disk and take out drivers by yourself (look for *.ko files). But then you'll probably need some tinkering to update initrd/initramfs/bootscripts/whateverSUSEuses to make your computer use them on boot.
    Also, run `modinfo' on those .ko files and checkout 'Lisence' entry. I would really like to know what it says.

    3. After all, the RAID is software RAID anyway. I really do not think that mysterious driver will provide better performance than regular aic7xxx + Linux software RAID. You will also have hardware-independent setup if you do it in aic7xxx+LinuxRAID way.

    By Blogger Hai Zaar, at 11:11 AM  

  • 1. When you use aic7xxx driver, you should see your drives as sda and sdb (or similar), even if you've defined them as RAID1 in BIOS. You should see their partition table as well. Try to access them readonly - its harmless.

    2. About fault tolerance: there are two cases:
    a. Your boot partition does not sit on RAID. In this case, you have full tolerance. Moreove mdadm have monitoring mode, so you can configure it send send email(s) if something has happened with your RAID. With more scripting you can get SMS alerts, etc..
    b. Your boot partition does sit on RAID. Such case needs some more care. BIOS knowns to boot from first disk, so if it fails, BIOS usually will not continue on next reboot and require intervention.

    Also make sure to install GRUB on both drives. You may want to check out http://www.linuxsa.org.au/mailing-list/2003-07/1270.html

    After all, any solution with this card is _software_ RAID, i.e. you'll get same fault tolerance level in either way. Its just the matter which drivers you push in.

    About the troubles with a320raid - first let me know if you are going to continue to inverstigate the topic.

    By Blogger Hai Zaar, at 5:11 PM  

  • Well, I see you a lot of free time then :)

    Actually, I've used SUSE only for a half year, and that period ended in July. So I can not help you with SUSE OS release information.

    Before you try to insmod the driver, make sure that modinfo reports the same vermagic as your kernel have. Anyway, before reporting further problems, please post output from:
    uname -a
    rpm -qa |grep kernel
    modinfo <.ko file you try to insmod>

    By Blogger Hai Zaar, at 9:24 PM  

  • Congratulation, first of all!

    I'm sure you could have done this without reinstalling as well, but since it works...

    One more time - major work load for RAID controller is to calculate where the blocks of data go, checksums, etc. If this is done by the driver, and not the hardware chip itself, the controller is pretty much 'software'. That's why I think you will not get any speed bonuses, compared to LinuxRAID. That's why the driver is distributed in binary mode only - it contains all the proprietary logic, what should be implemented in hardware. See yourself:
    modinfo ./a320raid.ko
    filename: ./a320raid.ko
    description: "Adaptec a320raid HostRAID driver v3.00.057"
    author: "Adaptec Inc."
    license: "Adaptec"

    The obvious contras of a320raid way are:
    1. You are using driver which is not widely tested by comunity. In fact I have no idea where SUSE has took it from, since Adaptec did not release such software.
    2. What about x86-64 (64-bit) support?
    3. What about diagnostic utilities / falure alerts?
    4. You are "marrying" with particular vendor for no reason.

    This is just an advice. Your house - your rules.

    May the RAID be with you :)

    By Blogger Hai Zaar, at 9:33 AM  

  • Once again - all of the logic is done by a320raid modules itselft and not he hardware. I've had the same story with HightPoint hp366.

    Its just like WinModem!

    See here (look at the second post)
    http://sysadminforum.com/showthread.php?t=321854

    There is complete article on the topic, but its in Russian:
    http://www.sensi.org/~alec/unix/redhat/raid_320.html
    Translate it to English with
    http://babelfish.altavista.com

    By Blogger Hai Zaar, at 12:41 PM  

  • I think the topic is exhausted. Lets stop before we go down to flame :)

    As afterword, I'm glad if I've managed to help you in any way.

    By Blogger Hai Zaar, at 7:14 PM  

  • I have an x236 (8841PDH)IBM Server which runs under OES Sp2 (a320raid Driver).
    But the ULTRIUM Streamer is not found under Linux. Either it's no found by lsscsi or it's found because I switched the Channel to HostRaid Enabled and I get I/O Errors when I access the STreamer. Do I have to switch HostRaid on or off ?

    Thanks for any help !:)

    By Anonymous Anonymous, at 11:31 AM  

  • I've never used a320raid driver. The only driver I've used was native linux "aic79xx" driver with Linux-RAID on top of sda+sdb.

    From what you write, it looks to me like this:
    Switching Channel to "HostRaid enabled" will give up that channel to HostRaid driver, and if you get error, then probably it either bug in a320raid driver (that it can not handle SCSI tapes), or a320raid just tries to use your tape as disk (i.e. its just "not supported" configuration)

    Now, if you do not set Channel to "HostRaid", then on the one hand - a320raid does not acquire it, but on the other hand, Linux SCSI subsystem does not see it as well.

    So, if I were you, I would try this:
    1. Try to load BOTH a320raid and aic79xx - sounds crazy, but who knows - may be Adaptec people are _that_ smart :)
    2. Dump a320raid at all and use native aic79xx with Linux-RAID (from what I've find out - performance will be the same). This way all of your SCSI hardware will work for sure.

    By Blogger Hai Zaar, at 12:08 PM  

  • So, if I were you, I would try this:
    1. Try to load BOTH a320raid and aic79xx - sounds crazy, but who knows - may be Adaptec people are _that_ smart :)

    IBM says in the Installation Guide for Suse OPen Enterprise Server to use the following Boot commandline:

    insmod=a320raid brokenmodules=aic7xxx insmod=aic79xx

    But when installed the aic79xx driver is neither loaded nor under /lib/modules


    2. Dump a320raid at all and use native aic79xx with Linux-RAID (from what I've find out - performance will be the same). This way all of your SCSI hardware will work for sure.

    If I just just use

    brokenmodules=aic7xxx insmod=aic79xx

    I see sda,sdb,sdc,sdd (i have 4 disks configured to be 2 raid 1's)
    Now I could configure a softraid /dev/md0 and /dev/md1 but that's not what you're thinking of, right ?

    By Anonymous Anonymous, at 2:29 PM  

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