vSphere Storage Appliance

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  • 1.  Delocalized storage: minimum wan requested performance

    Posted Mar 21, 2011 12:09 PM

    Hi, hoping this is the right group, I need to know if a delocalized storage (iSCSI storage which is in another datacenter different from the hosts) is safely usable for vm.

    We have a datacenter with hosts (3) and an iSCSI storage and the client is planning to put a second iSCSI storage but outside (connected by wan). The networking performances are about 50 - 70 ms (ping to reach the servers of the second location) I wonder if this second storage could be able to guest some vm (about 15) and safely act in a FT scenario.

    Can you help me?



  • 2.  RE: Delocalized storage: minimum wan requested performance

    Posted Mar 21, 2011 03:07 PM

    Is the question about the vSphere Feature FT (=Fault Tolerance) or is it merely the general Term and you just want to know whether iSCSI over WAN might be feasible ?

    If you're up to vSphere FT, i have only tested this with lab vms with quite good results up to 200 ms (virtual) latency, after that thing went downhill - but this may have been due to my (software) latency tool.

    Nevertheless the Primary VMs have been quite reasonably throttled down when we put some load on them since the bandwidth requirements shot through the roof.

    Have a look at http://www.vmware.com/files/pdf/partners/academic/fttech.pdf page 17ff "5- Performance Evaluation" for some FT specific values.

    Considering iSCSI async mirroring across WAN links you should be good to go - as long as the manufacturer of your box tells otherwise.

    I've successfully run an Openfiler drdb over a 250ms WAN link in async mode for redundancy stuff.

    If it would have been necessary i'd just start VMs over there on a quick replacement box, but running them locally from remote storage is something that might not work due to the quite high latency issues. At least not for production environments.



  • 3.  RE: Delocalized storage: minimum wan requested performance

    Posted Mar 21, 2011 04:50 PM

    Thanks a lot for suggestions.

    And yes, I'm trying to prepare a feasibility study about a long-distance FT.

    Unfortunately we speak about a production environment (not so many vm - 12 or 15 - all servers but no one with continuous high loads).

    The storage should be Dell MD3200i or Dell Equallogic PS 4000X.

    I wish I could determinate if the syncronous data replication of Equallogic is useful in the case of first storage failover or not.

    The document is very interesting but I haven't yet find anyone who had experienced with this kind of scenario



  • 4.  RE: Delocalized storage: minimum wan requested performance

    Posted Mar 22, 2011 09:35 AM

    Hi Vinz,

    sorry i cannot give you more hands-on experience than just some basic lab tests and "proof of concept" tries.

    I did not even dare thinking about FT over WAN :smileywink: But please keep us informed about the outcome of this project ... i'd really like to know what's necessary to do this.



  • 5.  RE: Delocalized storage: minimum wan requested performance

    Posted Mar 23, 2011 12:04 PM

    Hi, I just have read the thread at http://communities.vmware.com/thread/243101 which is quite similar to my problem.

    I wonder if some improvements have been made with the last vSphere release.

    From that discussion it seems there is no possibility of efficient FT or HA with the secondary storage (that is vmware hosts cannot use the secondary stoarage for data protection) and that it can be only used for pure data replication. Isn't it?



  • 6.  RE: Delocalized storage: minimum wan requested performance

    Posted Sep 17, 2012 01:12 PM

    Good suggestion.