BUILD (2)Samsung SM951 RAID 0 for VM Storage

[Syris]

I have a big pool that holds my home media, back ups, etc. I'm thinking about making an all flash pool for VM storage and would like to verify that I'm not overlooking anything.

I have read the following posts:
http://hardforum.com/showpost.php?p=1042115519&postcount=8
https://forums.freenas.org/index.ph...xi-nfs-so-slow-and-why-is-iscsi-faster.12506/
https://forums.freenas.org/index.ph...to-present-two-ssds-in-a-raid0-to-esxi.19473/

My understanding is that in order to get good performance without a SLOG it is necessary to set sync=disabled, which carries the risk of corrupted VMs/pool.

If that is the only risk I'm fine with that. This is for a homelab, all VMs backed up on and off site daily with Veeam(and I can live with any loss from 24 hours). My rig runs on a big UPS that is setup for graceful shutdown of VMs in extended power loss scenarios.

So my plan is to get:
(2)M.2 PCIe SSD M Key to PCIe X4 adapter
(2)Samsung SM951

Set them up in freenas as RAID 0 and disable sync writes on the pool. Than if I ever have power loss and corrupted data/pool I'll restore from backup. Got 20gbps networking in the works, so network shouldn't be a big deal. Will these adapters / SSDs work in FreeNAS/FreeBSD 9?

 

[jgreco]

I believe the SM951 is the OEM version of the 950 Pro, and the 950's been working fine here for awhile now as an L2ARC device.

I don't suggest trying to maximize for space even with SSD; plan to leave some space free on your pool.

That's all I'm willing to type out on a cell phone but there's probably more to be said..

 

[Syris]

Well shit. Didn't even realize that. Looking again I should probably use (2)950 pros (better write speeds and warranty). Thanks for the quick info while your mobile. Would really appreciate any other thoughts you have when time allows.

 

[jgreco]

Okay, anyways, so without some idea about the rest of your system, some general thoughts:

1) The NVMe stuff is probably way overkill unless you're doing 10GbE.

2) Without some form of redundancy, you run other risks of VM corruption because ZFS will simply err on the blocks that it cannot read and cannot recover from redundancy.

3) With those two issues in mind, there's a possibility that perhaps you should be considering instead a setup with some SATA 850 Evo's (about 1/2 the cost). You could get four 850 Evo's and put them in as two sets of mirror vdevs, and gain your redundancy. ZFS will let you read from both sides of a mirror to increase read speeds, though it won't be as fast as the 950. Write speeds would be reduced, but still fast.

Also, be sure that you're planning to leave some available space on the SSD pool. ZFS doesn't do so well with a full pool.

 

[Rand]

Just make sure you provide ample cooling as the NVMe SSDs seem to get quite hot and throttle.