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Thread: iSCSI target for Zimbra, ESXi vs dedicated machine vs VMWare Server local install?

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    Default iSCSI target for Zimbra, ESXi vs dedicated machine vs VMWare Server local install?

    Hi everyone

    I'm finally getting round to trying to evaluate Zimbra (I really don't want to renew our SBS 2003 licenses) and I'm looking at hardware/virtualisation.

    I'm mainly confused/concerned about the storage side of things.
    We have a hardware RAID card (3Ware 9690SA-8i) with 4 spare drive bays in the backplane which I was planning to use for a zimbra RAID 10 array.
    However this machine is currently our shared files NAS (Samba/Netatalk) and our intranet database system (Apache/PHP/MySQL)

    I have already tried Xen but found a problem with my Tyan motherboard which would only boot with a garbled boot screen. Tried OpenVZ too but couldn't get the memory allocation correct to prevent Zimbra Java VM errors.

    Option A:
    - Install Openfiler on the big NAS box and export the storage as iSCSI targets (or maybe configure the targets manually under CentOS if I'm feeling brave)
    - Build a new beast box for ESXi and run 3 VMs (zimbra / shared files / intranet DB)
    - Connect the 2 machines via gigabit ethernet directly, bypassing the network switch (or maybe on a separate VLAN, not used them before) so the storage traffic is isolated from the rest of the network

    Option B:
    - Configure iSCSI targets manually under CentOS on the NAS box
    - Run our shared files and intranet DB on the NAS box as we do currently
    - Build a dedicated Zimbra box that mounts the iSCSI storage
    - Connect the 2 machines via gigabit ethernet directly, bypassing the network switch (or maybe on a separate VLAN, not used them before) so the storage traffic is isolated from the rest of the network

    Option C:
    - Install VMWare Server on the big storage box and run Zimbra in a CentOS VM accessing the storage by SCSI passthrough
    So everything's running purely on one machine, but VMWare Server I/O performance is another concern

    I like the idea of option B the most... it's simple with no virtualisation bottlenecks (or potential bottlenecks) and all configured ourselves.
    But I worry how complicated iSCSI targets and multi-pathing are to set up manually. It seems to be ok from a few guides I've read, but performance tweaking could prove difficult.
    Also means I could dedicate some RAM as a ramdisk for the anti spam/virus definitions (I've heard that can be beneficial).
    And I'd like to stay away from large VM disk files and keep everything as a raw file system - so I can just mount in case of disaster.

    Then 2nd is option A, and VMWare Server would be my last option as I've heard I/O performance can be slow and I'm concerned about stability of VMware Server... random freezes etc.

    On to my questions:
    1) Should I be worried about iSCSI latency compared to directly connected storage when using Zimbra?
    We're a small business of 15 users all with relatively Exchange mailboxes of 2-8GB.

    2) For option B... I would be looking to mount the zimbra iSCSI target as /opt
    Zimbra will the only thing that will be running on that server so that should mean anything Zimbra-related (mail store, logs, settings etc) will all be stored on the iSCSI storage and not locally.
    Is Zimbra completely contained in /opt/zimbra or does it keep anything elsewhere on the system?

    3) With ESXi, could I store the whole VM on an iSCSI target?
    Or would it be better to just have Zimbra or the mail store stored on iSCSI and the rest of the OS on a local internal HDD?

    4) Would iSCSI targets in ESXi be a better option than VMWare Server's (apparently) relatively poor I/O performance with local storage?

    It seems a bit pointless creating a RAID 10 array, if iSCSI bandwidth is going to be the bottleneck.
    I've also read that iSCSI performance with ESXi can vary... apparently sometimes its better to use the iSCSI initiator in the guest OS rather than in ESXi. So that's another reason I'm tempted by option B.

    What does everyone reckon?

    Cheers, B
    Last edited by batfastad; 12-22-2009 at 06:25 AM.

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