FreeNAS as ISCSI Target for HyperVisor - Advice Needed

[bert386]

Hello there
Long time freenas follower, first time user.

I am looking to setup a freenas box as an ISCSI Target for a HyperVisor machine.
Hardware: Dell PowerEdge 2950, 6 x WD 500 GB Sata Drives, I am looking to setup the RAID card in pass-through. FreeNas will probably live on a USB Stick.

I am looking for recommendation on the best configuration for hosting HyperV machine files.
Any pointers on best RAID setup would be great, as well as any other general caveats and tips.

Thanks in advance!

 

[bert386]

Bump...
Anyone? No one?:(

 

[framewrangler]

bert,

You're going to have better luck here if you come up with detailed and direct questions. On your raid question, go with the most performant solution that provides the data reliability and capacity you can live with. If you can't satisfy all 3 requirements with your existing hardware, then get new hardware.

 

[jgreco]

Best RAID setup is ... not. Use mirrored with iSCSI for much less unhappiness and much better performance.

 

[framewrangler]

Does the freenas community not consider a stripe of mirrors ( raid1+0) to be raid?

 

[jgreco]

The inconsistent use of terms by n00bs is a real problem. Even the conventional storage market is inconsistent in what various "RAID" terms mean.

"mirrored" is not ambiguous. Nor is "several mirror vdevs".

 

[framewrangler]

I guess I'm failing to follow you here. In my experience the definition of raid10 has been pretty consistent between manufacturers. If the inclusion of zfs to the equation suddenly changes the terminology then that's fine by me. I'm just trying to ensure that my perceptions line up with others' realities. Now I know.

 

[louisk]

I have zero experience with hyperv (I use ESXi), but I'm using zvol to serve up iSCSI balanced across 2x 1G connections. The zvol has a dedicated pool of mirrors with 6x 256G SSD. Performance isn't bad (considering its iSCSI and 1G connections).

 

[jgreco]

ZFS doesn't offer RAID5, or RAID6, or RAID7, or RAID10, or actually a lot of that. ZFS offers things that may loosely be similar to those things in some ways, under some conditions. For example, with RAID5, you can calculate out which blocks on the drives are parity blocks. ZFS has no idea, until it writes a block, because the parity blocks are basically just appended to the data blocks, which is very un-RAID5-like, except that it still ends up roughly distributing the parity, so it sure ain't RAID4. And (at least in the context of this discussion and RAID10 vs multi-vdev mirrors) ZFS does not offer striping, but it does offer you the ability to add multiple vdevs to a pool, and all other things being equal, it will write data to both vdevs, which kind of seems like striping but isn't. Because if you add an empty vdev to a full pool, all writes will tend to flood the empty vdev. Which is what you want, and which is smart, something RAID10 isn't.

ZFS does support mirroring, which you would identify as RAID1, which is in fact pretty much the same thing. But if we call that "RAID1", then people call "RAIDZ1" by the wrong name "RAID5", which it isn't. Or they get confused because "what the F is that Z?" So do everyone a favor and don't try to rationalize ZFS's abstractions into common RAID terminology, which is only somewhat standardized anyways, a statement I'm not going to bother defending because I lived through it all.

It is better just to call things what they're supposed to be called.