8x 4TB Raid6 Setup

[StefanBP]

We're currently running a Raid6 Setup based on Windows Server on a DELL PowerEdge R520 (8 HDD Bay). My Problem is that 2 of the hdd slots are blocked by the windows server (raid1) os. So i want to switch to FreeNAS (USB-Stick Installation) to free up the 2 blocked slots so i can use a 8HDD Setup.


Hardware:
DELL PowerEdge R520 (Date 07/2013)
Intel Xeon E5-2403 (4x1800MHz)
8GB DDR3-1600 ECC
PERC H310 Hardware Raid
8x 4TB WD Red


Used for:
Backup only, speed doesn't matter too much, we backup arround 250-500GB each night using SMB or NFS


My questions (because i'm new at FreeNAS Setups):

1. Is the DELL PowerEdge R520 system supported by FreeNAS ?
2. Should i use the hardware raid (and is this supported by FreeNAS) or should i use a software raid
3. What Raid type do you recommend? Raid-Z2 (Raid6) would be my choice


Thank you in advance!

Stefan

 

[HoneyBadger]

Hi StefanBP,

ZFS and hardware RAID controllers, generally speaking, do not get along. ZFS expects direct access to the disk rather than having to be filtered through a controller. Some controllers are usable if they allow what is called JBOD or passthrough mode.

While the PERC H310 supports JBOD/passthrough mode, it has a known, uncorrectable fault causing a performance drop in this mode. See here:

http://en.community.dell.com/support-forums/servers/f/906/t/19480834.aspx

If the write throughput limit (roughly 500MB/s) isn't an issue then this machine should work fine.

Regarding the RAID type, I would suggest a RAID-Z2 since your backup loads will be sequential writes. Write speeds will be roughly 6x a single drive. Quick edit on speeds - The 4TB WD Red benches out at roughly 140MB/s under 100% sequential write load. Six of them gives you a theoretical max of 840MB/s, enough that the H310 would be the next bottleneck after the network unless you're running 10Gbps.

 

[cyberjock]

I just read that article. I'm wondering if the H310 is running in a PCIe 1x mode. PCIe 2.0 offers 500MB/lane, and the limit is just shy of 500MB/sec... hmm.

Anyway, to the OP.. if you go this route PLEASE make sure that SMART works properly with your disks in JBOD, all caches are disabled for the controller, etc. HBAs are strongly preferred over RAID controllers, and if you want to twist a RAID controller to work in this function you may suffer zpool corruption. So tread carefully...

 

[HoneyBadger]

I just read that article. I'm wondering if the H310 is running in a PCIe 1x mode. PCIe 2.0 offers 500MB/lane, and the limit is just shy of 500MB/sec... hmm.

The read speed is unaffected by this bug apparently, so I wouldn't think PCIe width/lane count is the issue or it would be similarly capped.

 

[cyberjock]

The read speed is unaffected by this bug apparently, so I wouldn't think PCIe width/lane count is the issue or it would be similarly capped.

Very true. I didn't see anything about read speed being different, but I only read on it for a few minutes out of curiousity.

 

[Rand]

While the PERC H310 supports JBOD/passthrough mode, it has a known, uncorrectable fault causing a performance drop in this mode. See here:
http://en.community.dell.com/support-forums/servers/f/906/t/19480834.aspx
If the write throughput limit (roughly 500MB/s) isn't an issue then this machine should work fine.

This is not the case when used with LSI (16 atm) Firmware - at least not for me...
Just ran a test on 2 ssd's -> 750 MB dd speed on iostat and average
Checked total write speed of all disks (distributed over 2 controllers) -> ~1450 MB