Impact of having 1 datastore vs 2 for HA

[hbato]

Hi everyone,

I have a question for this scenario for HA.

A. One Datastore with HA

4 Tb iSCSI for shared storage (VMs and vmdk backup)

4 hosts

1 vCenter

das.ignoreInsufficientHbDatastore=true

B. Two Datastore with HA

3Tb iSCSI for VM

1Tb iSCSI for vmdk backup

4 hosts

1 vCenter

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The question would be what will be the impact of two setups and why? I can't seem to see the logic of having two datastore (in this scenario). It seems to be that the only reason for having two datastore would be to justify the minimum requirements for HA datastore heartbeat.

Regards, Harold

[vmroyale]

Hello.

Note: Discussion successfully moved from VMware ESXi 5 to Availability: HA & FT

Good Luck!

[depping]

Hi,

I guess the main thing to point out here is that if your store yourback ups on the same datastore as the originals how will you do a restore if the VMFS or LUN is corrupted? Although chances of that hapening are slim, I wouldn't take the risk!

Also, you could easily avoid the "two datastore cluster alarm" by setting the HA advanced setting "das.ignoreInsufficientHbDatastore" to true.

My suggestion: use 2 datastores and seperate your backup from the original VMDKs!

[hbato]

That is true, but for some reasons, this is all that we've currently got. Will there be a difference in having one vs two shared datastore when they both reside on a single storage?

[mcowger]

Yes - queues.  With only a single LUN, you've got only a single queue into that LUN, leading to longer queues and increased response time.

If you have the option, I'd even cut it down further, to 4x1TB volumes.

[hbato]

hmmm.. will that be a signicant performance loss? i'm talking about performance of a single shared datastore for heartbeat.

Regards, Harold

[depping]

no performance impact on a heartbeat datastore from a "heartbeating" perspective.