ZFS hardware RAID, no JBOD

[Mikael Hagberg]

Hi!

I'm having trouble choosing between UFS and ZFS for my 5x2TB system.
From the start it was 4x2TB, and now im unable to expand it so im thinging what to do?

This is my system:
FreeNAS Build FreeNAS-8.0.4-RELEASE-p1-x64 (11059)
Platform Intel(R) Core(TM)2 Duo CPU E8500 @ 3.16GHz
Memory 8176MB
http://www.supermicro.com/products/chassis/2U/826/SC826E1-R800U.cfm
http://www.supermicro.com/products/motherboard/Xeon3000/X48/X7SBU.cfm
http://www.supermicro.com/products/accessories/addon/aoc-usas-h4ir.cfm

Harddrives:
7x500GB iSCSI
5x2TB UFS

My RAID-card does NOT support JBOD, and i can't run all my harddrives without it (backplane).

Is it bad if i make a new 5x2TB ZFS volume? if not, is it still better than making a new 5x2TB UFS volume?

 

[SnorreSelmer]

When I installed the RAID-controller in my server I had to dump the entire server content and re-make the entire array to get full usage.
You can expand a zpool by adding another vdev to it. The problem I had was that I ran a 4+2 raidz2 and my only option was to add a 2+2 raidz2 to maintain the double parity all over. The whole point of adding four more drives was to get get them all as storage-space.

A way around the "no JBOD support" problem would be to add each disk on the controller as a single-drive RAID0 and then soft-raid them in FreeNAS using ZFS (if you can).

PS: You definitely want ZFS over UFS!

 

[Mikael Hagberg]

thanks for your reply.

when you read: http://doc.freenas.org/index.php/Hardware_Requirements
it says:
"NOTE: It isn't recommended to mix ZFS RAID with hardware RAID. It is recommended that you place your hardware RAID controller in JBOD mode and let ZFS handle the RAID. According to Wikipedia: ZFS can not fully protect the user's data when using a hardware RAID controller, as it is not able to perform the automatic self-healing unless it controls the redundancy of the disks and data. ZFS prefers direct, exclusive access to the disks, with nothing in between that interferes. If the user insists on using hardware-level RAID, the controller should be configured as JBOD mode (i.e. turn off RAID-functionality) for ZFS to be able to guarantee data integrity. Note that hardware RAID configured as JBOD may still detach disks that do not respond in time; and as such may require TLER/CCTL/ERC-enabled disks to prevent drive dropouts. These limitations do not apply when using a non-RAID controller, which is the preferred method of supplying disks to ZFS. "

So every harddrive in RAID0 is not recommended...
But if i make a hardware RAID5 with my 2TB drives and make that volime ZFS? Is that wrong? Will i be able to expand the volume later?

 

[louisk]

It may not be recommended, but it works fine. I have 8x2T with RAID0 hardware managed by ZFS at home. No issues.

 

[Mikael Hagberg]

I got realy crappy speeds using hardware RAID 5x2TB RAID 5. and then format the drive in zfs..

Have to try making all the drives RAID 0....

 

[SnorreSelmer]

At Opera Software I know they run single-drive RAID0 "arrays" to get the same effect as JBOD on their RAID-controllers (high-end RAID-controllers rarely have JBOD because no-one in their right mind would use JBOD in a corporate environment).

Also, you should NEVER make a RAID5 array and then format it as ZFS. ZFS wants full access to every single drive to make it's own array.
Running ZFS on top of a RAID-array would be like running a software RAID-array on top of a hardware RAID-array.