Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

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
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
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 '14 at 11:02
@JohnGardeniers P400/P410i doesn't support device passthrough, i.e. TRIM/discard with RAID arrays will be unsupported, so, if you have SSD's, they might and die very soon in intensive applications. If application is not that intensive - don't use SSD's. – GioMac Jul 7 at 19:20
up vote 2 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
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
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
This is wrong. There's no way to present RAW drives from a Smart Array controller. – ewwhite Nov 4 '12 at 7:45

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

It should also be noted, just because I just killed 7TB of data by following LapTop006's, well, lets call it "personal opinion", that a P400 Controller would expose unassigned disks as JBOD, that this is nothing but a guess, and it is false, at least for my P400. There may be other controllers behaving like LapTop006 said, the P400 does not, at least not with the original firmware (V2.75).

I learned this the hard way today when trying to bring over a 6 disc software RAID-5 from a machine with a faulty 6 channel SATA RAID controller. They had always been part of a software RAID, the RAID functionality of the ICH9 "Fake" RAID controller had never been used anyway.

The target machine didn't have enough SATA ports, so I thought, well, no problem, it is a SOFTWARE RAID anyway, why not attach the disks to a P400, the disks would - if the controller behaved like stated - appear as JBOD, and the OS would - like it had done many times before when I moved software RAIDs from one machine to another - recognize the RAID.

In my case, however, the P400 did recognize the disks as new and - without seeking my confirmation - it did auto-create a RAID-5 array at the controller level as soon as I powered up the computer. Bye-Bye software RAID.

I brought the disks back to the original machine, but the RAID had already been corrupted, the OS saw 6 empty disks now.

Bye, 7TB of data.

Damage already done, I played with the disks a little bit. Back at the P400 equipped machine, I deleted the unwanted RAID-5, the disks didn't appear at the OS level. I had to create 6 RAID-0 disks, and they appeared - all empty, however.


  • The P400 does not pass unassigned disks to the OS.
  • You need to create RAID-0 configs to get the disks through to the OS.
  • Saving the RAID-0 config (or any other P400 config) will empty the disk(s).
  • The P400 auto-config may have killed anything on the disks anyway, by creating a RAID-5 without asking permission.
share|improve this answer

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

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

Your Answer


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.