I have just created my first TrueNAS install. My intention is to have a RAIDz-2 pool that is fully shared via iSCSI to a Windows server.
However, I hit some questions I was unable to answer from the usual Google searches:
Is it better to create a ZVOL or a dataset to share via iSCSI?
When creating the iSCSI share on TrueNAS, I’m asked for size. The recommendation is to not specify more than 80% of pool size. Why is this? I’d like to use all available storage in the pool for the iSCSI share - is this unwise for some reason?
I have succesfully mounted the iSCSI volume on my WIndows server. What file system would you recommend, NTFS or ReFS? I’m aware of the differences of the FS types themselves, but not in combination with the ZFS foundation. Is there a clear favourite here?
iSCSI works best with mirrors and less than 50% occupancy.
If you want to use raidz2 for space efficiency go for SMB or NFS. Then you might safely fill your pool up to around 80%, tough at some point performance will suffer; then around 90% performance will go down the drain as ZFS switches to a different allocator, and you should never ever reach 100% (=locked pool!).
You’re right, that’s not good for my use case at all. Thanks for making me aware of the issue.
I don’t want to use SMB directly because I don’t want to join the TrueNAS to the domain. But, if I understood correctly, using iSCSI on ZFS would basically negate some of the principal benefits of ZFS. That’s not what I want either.
To be honest, I have no idea how to proceed at this point.
Is there another option I haven’t considered yet?
I have…
a Windows environment with user and share management
a stand-alone machine with TrueNAS (under construction)
on the TrueNAS, 7 HDDs at 16 TB each
1G network between server and NAS as well as to the clients
I want…
resiliency for two failed drives (thus my approach with raidz-2)
SMB shares to the clients, permissions controlled by the Windows ActiveDirectory
a focus on storage, not “live work” (few database, VM etc. operations). Performance should be enough for e.g. photo editing, but video editing etc. is not required
few parallel users working at once (mostly just one or two)
overall performance need not be terrific, since the slow network would limit that anyway
iSCSI would have been the perfect solution, but I understand the problems with that. Is there another way to have my cake and eat it, too?
I’m looking into NFS right now. Maybe this will get me somewhere, but I have no experience with a combined environment like that. Well first time for everything I guess.
SMB with Unix would mean Samba, doesn’t it? I don’t know much about Samba, just enough to know that I don’t trust it. No exact reason for it, just a gut feeling.
For example, Samba supports up to “Domain Functional Level” 2016 AFAIK, not above. If I joined a Samba server to my domain, I would be limited as to how I can raise the level - should I ever want or need to. I don’t want to introduce restrictions to the domain.
Read more about SMB—even though it’s from Microsoft it’s possibly not as bad as you picture it (and THAT is coming from a M$-hater).
And possibly also read more about iSCSI because it is certainly not as “perfect” as you think (to begin with: high RAM requirements).
Honestly, your requirements map straight on to SMB share(s) from a raidz2 while iSCSI looks totally inadequate.
Two 3-way mirrors and a spare, for a total of 16 TB usable shared with iSCSI from your 128 GB RAM NAS. “Perfect solution”?
I followed your suggestions and changed my storage to pure SMB shares, with the TrueNAS joined to my Active Directory domain. All worked well (eventually, I hit a few known bugs and other snags in the process) and the storage is performing great so far, easily able to saturate the network link.
