Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

I'm planning to use ZFS on my system (HP ML370 G5, Smart Array P400, 8 SAS disk). I want ZFS to manage all disks individually, so it can utilize better scheduling (i.e. I want to use software RAID feature in ZFS).

The problem is, I can't find a way to disable RAID feature on the RAID controller. Right now, the controller aggregates all of the disks into one big RAID-5 volume. So ZFS can't see individual disk.

Is there any way to acomplish this setup?

share|improve this question
2  
Disable hardware RAID in favour of software RAID? That just doesn't make sense to me, especially as you have such a well proven controller. –  John Gardeniers Jul 17 '09 at 4:49
1  
Well, this is IMHO debatable. But I think ZFS has clear advantages over pure hardware RAID. –  Arie K Jul 17 '09 at 6:35
    
@JohnGardeniers You obviously knew nothing of ZFS when you wrote that comment. If your lack of understanding has now been corrected, you may want to consider tidying up (deleting) your comment. –  Mark Booth Mar 12 at 11:02
add comment

4 Answers

up vote 3 down vote accepted

If you simply delete the volume in the RAID BIOS that exposes the disks directly in some versions of the SmartArray controllers. We always use the controller even with things like ZFS.

share|improve this answer
    
This is the right answer - just delete the array in the ACU, that way the BIOS just sees the disk. That said are you SURE you don't want it managed by the P400? they're a damn good card. –  Chopper3 Jun 21 '09 at 14:46
    
Aha, so this bring back ol' software vs hardware RAID war :) Should I combine both setup: ZFS' pool on top of single RAID-5 (or even RAID 1+0) volume exposed by P400? –  Arie K Jun 21 '09 at 16:18
6  
There are advantages to letting ZFS have the raw disks over a hardware raid controller. For one if you have a disk go bad ZFS will only need to rebuild the actual data rather than the entire block device speeding up rebuild and reducing the possibility of running into another problem while rebuilding. By giving ZFS the entire raw disk ZFS also manages the drive cache which improves efficiency. Third ZFS will properly detect and correct IO errors due to its exhaustive data checksumming. Because of this I wouldn't put a hardware raid inbetween ZFS and the Disks. –  3dinfluence Jun 22 '09 at 3:41
1  
Adding my thoughts here, since this came up in my search results... In my case, I'm using an HP Smart Array P212. It looks like this controller can not present the raw disks (no jbod mode). If you delete all raid volumes, it just doesn't present anything to the OS. I want to use linux software raid (md raid) because: 1) no raid 6 support on this controller (may be able to purchase a license to add this) which I want since I'm attaching 24 drives, and 2) I'm using desktop drives, which I hear md raid handles desktop drives better than enterprisey controllers that expect enterprise drives. –  James Jan 3 '12 at 14:32
2  
This is wrong. There's no way to present RAW drives from a Smart Array controller. –  ewwhite Nov 4 '12 at 7:45
add comment

The other option is to create each disk as a single-disk RAID-0 array (yes, it should let you do this). Then ZFS will see all the indidual disks.

The 'technical' name for the option you're looking for is called JBOD - Just a Bunch of Disks.

share|improve this answer
    
Would this introduce additional overhead on the RAID controller? –  Arie K Jun 21 '09 at 16:20
    
Don't know, I doubt it, but it looks like the other answer by Laptop006 is more appropriate as he seems to have more experience with this scenario. –  Mark Henderson Jun 21 '09 at 21:24
add comment

It is not possible to disable the RAID functionality of HP Smart Array controllers.

A common "solution" to this problem is to create single-disk RAID-0 volumes at the controller level. This is not a good solution and is not equivalent to a JBOD arrangement. There's RAID metadata on the disks, and the failures will produce unexpected results.

In this case, be careful with the Smart Array P400 single-disk RAID 0 setup. If you have a hotplug event (disk failure/drive removal), ZFS won't recognize the new disk without a reboot. There's no true JBOD setting on these cards.

Using a dedicated SAS HBA is the right path.

share|improve this answer
add comment

I simply moved the internal SCSI cable from the smart array card to the on board SCSI Controller located on the system board. This gave me access to the raw disks.

share|improve this answer
    
That may apply to older pre-G5 ProLiant servers. It's not valid on modern systems because they no longer have onboard SCSI. –  ewwhite Mar 6 '12 at 19:01
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.