Zimbra - NFS vs. iSCSI

We are going to be migrating our mail server from postfix/courier to Zimbra over the next few months. We've run a prototype server over an iSCSI LUN exported from a Dell Equallogic quite successfully. The Equallogic isn't our 'production' SAN, a NetApp FAS 2050 is.

One of the problems with having a system based on an iSCSI LUN is lack of flexibility. What if we need to resize without having to bring the whole system down? I feel that putting the Zimbra datastore on an NFS export would help in terms of

• flexibility of resizing at any time without downtime
• snapshots of past file revisions are easier to access
• no need to worry about the filesystem getting corrupt / no fsck'in

Cons of switching to NFS

• speed
• reliability (?)
• speed

The question is, whether or not Zimbra (which runs a whole stack of daemons including spamassassin, jetty and most importantly MySQL), will be reliable & stable enough to run under NFS - are we setting ourselves up to lose data running MySQL under NFS? If we do choose to run it under NFS - what can we do to tweak performance?

Resizing an iSCSI LUN on the fly on a NetApp is no big deal, we do it all the time. The only gotcha is in the level of support of your file system for resizing a block device on the fly. That said the ease of using snapshots and WAFL log file system are two big benefits for NFS on a NetApp.

While I don't deal with Zimbra or any other mail servers in my line of work this sounds awfully like the FC/iSCSI vs NFS debate for ESX. Running ESX on NFS against a NetApp is a no brainer mainly for the snapshots and WAFL reliability. Speed has not proven to be an issue. There are plenty of benchmarks showing that 1GBps NFS can hold it's own against 4GBps FC for ESX (this is mainly due to the highly random nature of ESX I/O traffic).

If you want so go even faster you can always stick a 10GBps NIC in a NetApp (Not sure if a 2000 series can do 10GBps though...) and it can blow away any (8GBps) FC card you can buy today.

There is a posting on the Zimbra forums about this very topic. The poster there went with NFS.