How well can NexentaStor work with VMware?

Posted on 2011-04-30
Last Modified: 2012-05-11
I  am thinking of replicate SANs across WAN sites.
Say my primary datacenter at HO: All servers are virtual machines in VMware environment, the primary SAN (SAN_p) is provided by NexentaStor at site HO.
And my secondary SAN (SAN_s) is also provided by NexentaStor at site B.

Q#1. Is NexentaStor SAN able to run with VMware Site Recovery Manager (SRM)?

Q#2. Is NexentaStor able to replicate SAN_p to SAN_s over 3Mbps WAN? How efficient is such replication?

Q#3. If SAN_p is destroyed at Site HO, is SAN_s good enough to bring up the same datacenter state at Site B given that I have the same ESX environment as site HO?

Q#4. Is NexentaStor able to work with VMware ESX to 'flush' virtual machine memory state to SAN when 'synching' SAN_p to SAN_s?


Question by:richtree
    LVL 46

    Accepted Solution

    IF you go down that path, you really need to make sure you use direct i/o.   It is vital for performance and data integrity reasons that you let the solaris O/S do all physical I/O, using software RAID.
    That is because of things like
       * zfs uses variable-length block size
       * flush-after-write
       * vmware & RAID will do pre-fetching, which is counter-productive because ZFS knows exactly how much I/O it needs, and will need so any extra reads done by VMWARE to help you actually hurt you

    But it will work well in vmware, just make sure you just let vmware deal with the O/S only, not the data that is being presented to the network.  Also give it LOTS of RAM.  The solaris kernel uses as much ram as you will let it as a read cache to improve performance.   A small SSD is also a good idea for zpools as cache.  

    Author Comment

    What do you mean by 'direct io'? Does it mean 'passthrough' or similar to VMware RDM?
    Does it make sense to recover site using NexentaStor replication?
    Anyone else is going this path?
    I hear people achieve this goal by going with VMware SRM and NetApp SAN replication.
    LVL 46

    Assisted Solution

    Yes, same as passthrough.  You want the disk controller to be married to the virtual machine, so only the solaris/nexenta VM has 100% access to it, and no other machines can see any of the disks or even the controller.  

    Let nexentastor do clustering / replication, backup, etc...

    I'm ware of some sites with hundreds of machines running nexenta, and they don't use SRM.  I am not saying that VMWARE+SRM+NEXENTA won't work, or will work poorly, it is just that vmware brings constraints that cancel out many of the benefits.  In interest of full disclosure, I am not aware of anybody that has deployed 100+ node SANs that stayed on the VMWARE+NEXENTA architecture after testing for a few weeks.

    If you want all of the features you described, you should carefully consider  blowing off nexenta completely and going with NetApp or a more traditional (and more costly architecture, if budget allows, remote replication is not the type of thing that people generally do with nexenta, and IMHO it is a kludge)
    LVL 116

    Assisted Solution

    by:Andrew Hancock (VMware vExpert / EE MVE)
    VMware SRM is not an absolute requirement for DR at a second site, it just makes it a little easier. But good WAN replication between SANs is a must, and NetApp have got this perfect with their SnapMirror product, which can also be bandwidth throttled by the NetApp filers.

    Author Closing Comment

    Thanks a lot.

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