DAS vs iSCSI for VI3

Dear All

We will be implementing 2xVI3 hosts(without VC) on Dell 2950. We have the following hard disks in caddies - 3x300GB 15krpm+ 2x73GBSAS

I have the following choices-(please correct me where wrong)

a) Forgo iSCSI alltogether as it has got management overhead + performance penalty. I am assuming given same hardware, DAS performs better. So, host A and host B run independant on DAS.

b) Make a nexentastor/openfiler target (on a unused dual core 2.4Ghz whitebox with SAS card and use the 3x300GB to present target). Then host A will have 73GB to boot VI and host B also will have 73GB to boot VI.

Which one is better - a) or b). Am I right in assuming that DAS will perform better than iSCSI target on same hardware?

With the above hardware, (ie, 2xDell 2950 + 1xDualcore whitebox) what will be the optimum config? We also have 6x250GB in Dell caddies lying around (can be used as additional storage in target or maybe in host a/b)

Thank you


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2 Replies

I would probably opt for the shared storage...even if there is a performance penalty. If your workloads are "typical", you'll never notice the performance hit. If you have seriously heavy loads, then you may. The advantages of shared storage -- in my opinion -- far outweigh the performance gains of local storage. With shared storage, you can move your VMs from one host to another very easily (without VC all you would need to do is shutdown/unregister on one host, register/startup on the other). This will allow you to balance your workloads between your hosts and provide you with some degree of fault tolerance. If one of your hosts fails, you can run (perhaps in a degraded mode) your critical VMs on a single host.Also, shared storage will make it much easier for you to expand your environment in the future. You'll be able to add additional hosts or upgrade your VI to include VC with VMotion, DRS, HA, etc.with minimal disruption.

I would recommend that you put your iSCSI network on a dedicated GbE switch - small ones are cheap and you'll guarantee bandwidth availability.

Ken Cline

Technical Director, Virtualization

Wells Landers

VMware Communities User Moderator

Ken Cline VMware vExpert 2009 VMware Communities User Moderator Blogging at:
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You also have to consider the cost of Vmware. If you're going to use local storage, you can get away with Standard Edition. If you go with shared storage, go with Enterprise Edition.

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