iSCSI design question

[lanlubber]

I've done some searching and can't find and exact answer to these questions.

Can iSCSI be setup to use storage from my existing NAS pool or do I need a dedicated pool for iSCSI? ZFS ok?

My motherboard will have a second NIC, can I dedicate this NIC to iSCSI communication only within FreeNAS? The FreeNAS iSCSI NIC will be on it's own switch connecting only to my ESXi server. (which I'm assuming will support a dedicated iSCSI NIC / network as well. )

This is for home use minimal performance requirements.

Thanks

 

[jgreco]

Of course iSCSI can be setup to use storage from your existing NAS pool. You may not want to do that, however. Your "existing NAS pool" is probably RAIDZ2 or something that isn't optimal for iSCSI; you probably want to look at posts I've written, about half of which seem to involve correcting bad iSCSI designs. Of course you can add another network interface for iSCSI.

 

[lanlubber]

Thanks for the info. My NAS pool will be RAIDZ2. I read through a couple of your posts. Without going too deep in the weeds (I took the server track through my career not the storage (SAN) track :)) this is more of a problem with the interaction (fragmentation, performance) between iSCSI, RAIDZ2, and ESX? Would I be better off skipping iSCSI and use NFS for ESXi? Ultimately what I'm looking for is to avoid local VM storage on my ESX box and take advantage of the fault tolerance capability of FreeNAS with RAIDZ2.

 

[jgreco]

No, in general RAIDZ2 interacts extremely poorly with block storage of any sort, whether iSCSI or NFS in nature. RAIDZ is great at storing long runs of sequential data. Mirrors are very efficient at storing random access data. There's no middle ground.

 

[lanlubber]

Great, thanks again....

 

[lanlubber]

I just ordered my parts and took your advice and will be creating a separate mirror set for my VMs used by ESXi. I have a couple more questions if you don't mind? Keep in mind any VMs I'm running are for home use and don't really need enterprise level performance. Am I ok using NFS or should I keep going down the iSCSI route for my VMs to run from? By default compression is enabled, should I disable this for a volume holding VMs? Thanks

 

[jgreco]

Some people prefer iSCSI and some prefer NFS. NFS gives you file-level access to the VM vmx and vmdk files, which is nice for some purposes. Both iSCSI and NFS have various ups and downs, most of which are relatively minor.

Compression is totally awesome for almost anything on ZFS, though "which compression option is right for me" is a more complex question. For every compressible block, you end up with more free space, which translates to extra write speed, and when reading, decompression may actually be faster than reading uncompressed data over the SAS bus, so reading compressed data may turn into a win there too.

 

[lanlubber]

Thanks again, I think I'll stick with NFS mainly for the reason you state above for file access plus I'm probably more comfortable with it than iSCSI.

 

[jgreco]

Two excellent reasons to make that decision, in my opinion.