MegaRAID JBOD substitute

Question

It seems that certain MegaRAID chips don't support JBOD (unfortunately).

I've read online that to make these controllers act as a pass-through, I should configure the disks in RAID0.

What RAID0 settings do you recommend?

Which MegaRAID are we talking about? – Nils Nov 27 '11 at 20:34 — Nils, Nov 27 '11 at 20:34

score 8 · Answer 1 · edited Apr 13 '17 at 12:14

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Are you trying to use the card for a software RAID solution like ZFS? Which controller are you using? If this is the case, using multiple RAID-0 logical drives will create an ugly situation if you need to swap a failed disk. The replacement drive will not be recognized until you reboot/reinitialize a new RAID-0 array containing the failed disk. It's not worth it. Use a proper HBA if possible, OR use the hardware RAID functions of the controller with ZFS (sometimes it makes sense).

Please refer to: ZFS SAS/SATA controller recommendations

edited Apr 13 '17 at 12:14

Community

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answered Nov 27 '11 at 15:05

ewwhite

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Exactly. I just finished to configure the 24 drives using megaraid's webios, a painful game. And yes, i will use ZFS. (i decided that 2 drives goes on raid 1 hardware for the os, the other are JBOD to ZFS). I'm using a 9280-4i4e, unfortunately i can't change it! – cedivad Nov 27 '11 at 15:29
There's a big downside to configuring multiple RAID-0 arrays using the controller you're using (this also applies to Dell and HP RAID controllers). If you DO lose a disk, it's the same as losing a logical drive. Your replacement disk won't be recognized until your reboot. E.g. you won't have hot-swap capabilities. If you're interested in running a ZFS-based solution the right way, use one of the controllers I linked to in my earlier post. – ewwhite Nov 27 '11 at 15:31
understood and received that i can't go this way. Thanks. – cedivad Nov 27 '11 at 15:35
[given the impossibility to change the controller], please look at this page: http://kb.lsi.com/KnowledgebaseArticle16511.aspx - maybe the red text is the solutions to my problems? =) – cedivad Nov 27 '11 at 16:02
Probably not. It's just a downtime risk. The system will run just fine. It just means you'll need a reboot if you have to replace a failed disk. That's all. – ewwhite Nov 27 '11 at 16:06
I just hope more people read this. :( – SvennD Dec 04 '15 at 09:36
@SvennDhert Why? – ewwhite Dec 04 '15 at 09:38
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My first large server (100TB) has LSI MegaRAID SAS 9271-8i, with 34 raid0 disks (on each disk) with ZFS (raidz2), 1 disk hiccup put the system down for 48h, a replacement raidcontroller and disk where needed to save it. RAID 6 on the card or another card with JBOD and nobody would have noticed... – SvennD Dec 04 '15 at 09:41

Skyhawk · Answer 2 · 2011-11-27T15:38:26.700

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Don't do this with 24 drives. Get a different controller. Anything based on the LSI 1068e (which is a bottom-of-the-line option for many Dell and IBM servers) will support JBOD. Dell calls it a SAS 6/iR and IBM calls it a ServeRAID BR10i.

edited Nov 27 '11 at 15:38

answered Nov 27 '11 at 15:27

Skyhawk

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Point is that, even paying, i can't change my controller. It's an OVH HG server. I contacted the support to see if they can do an exception, but i'm not optimist. Thanks for the tip. – cedivad Nov 27 '11 at 15:32

score 2 · Answer 3 · edited Sep 18 '17 at 02:17

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Untrue! Some of the MegaRAID cards (such as the raid controller that IBM rebrands as the M1015) do support JBOD passthru.

If you want to use JBOD mode I'd suggest these cards. Know a local IBM VAR? I'd recommend getting friendly with them - odds are they have a whole mess of these cards on hand.

edited Sep 18 '17 at 02:17

Victor

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answered Nov 27 '11 at 15:21

MikeyB

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Thanks, but i can't change my card! :( – cedivad Nov 27 '11 at 15:29

Per von Zweigbergk · Accepted Answer · 2011-11-27T18:06:21.487

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I run this exact setup. MegaCli has a useful option called something like CfgEachDskRaid0 which will configure every disk on the array as raid0, ensuring a consistent configuration.

It's not true that it's impossible to hot swap disks with this setup, although it is clunky to do so (especially because MegaCli itself is hardly a paragon of usability), basically involves deconfiguring the old raid array and reconfiguring a new one every time you want to swap a disk.

edited Nov 27 '11 at 18:06

answered Nov 27 '11 at 18:00

Per von Zweigbergk

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This is still a bad solution for long-term ZFS use. – ewwhite Nov 27 '11 at 20:44

score 1 · Answer 5 · answered Nov 27 '11 at 11:35

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On our MegaRAID card we just make each drive its own raid-0 array, however we rarely have more than one drive in this configuration and I have no idea how well this scales.

answered Nov 27 '11 at 11:35

Lamar B

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yes, it's the same thing i'm doing - let's hope it to work on 24 drives :( – cedivad Nov 27 '11 at 13:24

score 1 · Answer 6 · answered Nov 27 '11 at 20:37

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Can`t you simply switch off the raid-controller in the BIOS?

answered Nov 27 '11 at 20:37

Nils

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I wouldn't see any disk at all if I did so! – cedivad Nov 27 '11 at 20:41
I will try, but I'm dubios it will work... I will report it – cedivad Nov 28 '11 at 03:20
disabling boot from card is useless. – cedivad Nov 28 '11 at 13:08
An actual server where this would have worked would have been a Dell PowerEdge 2850 with PERC5i raid-controller. This raid-controller is being activated by a key. If the key is not present it will serve the disks as JBOD. Thus there is an option (if the key is present) to disable raid - and you will have JBOD instead. But that does not seem to be the case with "your" server. – Nils Nov 30 '11 at 20:37
It's a card inserted *on* the server, it's not an integrated stuff. thanks anyway. – cedivad Dec 01 '11 at 13:07

MegaRAID JBOD substitute

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