Do you have some feedback about Zimbra on iscsi storage (particulary Equallogic) ?

I'm looking for some information to help me in sizing and best practices , Raid Level, kind of disk SATA or SAS ?

I'll answer here (and not on LinkedIn).

It depends on many factors : number of accounts (provisionned & active), number of mails sent/received, "bare metal" or VM, etc...

yeah mailbox size and location of backups is also things you need to consider in sizing and choosing speed. we use iscsi and find its fine. Linux <-> linux only though.

One of their key features of Equallogic SANs, when you have several of them (SATA, SAS, etc) is the automagical balance of the data on different type of volume/disks depending on data usage.

This feature is directly integrated in ZCS, it's the HSM.

Whatever you do, make sure you have iSCSI initiator configured to queue if an error happens (you need multipath installed for that), I did not configure it at first and when you have a minor problem (network cable gets loose, whatever) you'l have to reinitiate the connection, which can lead to all sorts of troubles ...

in my case (as i use KVM machines which resides as well on the iSCSI, and inside the zimbra virtual machine another iSCSI connection to the mailstore) i had to reboot the KVM Host because reconnection did not work, or, reconnection did work, but the KVM's could not work anymore, they where frozen with I/O Errors.

So, make sure to test possible failures!