View 4.5 Local Replica Storage (SSD)

[WillUsher]

Hi All,

I've was reading the View 4.5 Referance Architecture document talking about storing the replica base images on local (ssd) storage and I was wondering exactly what got stored locally and what the implication were. Below is the image that I'm referring to:

So my quesiton is: Are the VM delta images stored in the local SSD storage (I would assume so, since the deltas have considerible I/O)? If so, I would have to assume that would prevent any DRS migrations from taking place. Also if the host were to go down, you would need to recompose all of the VM's that were living on local storage on another server?

Thanks everyone,

William Usher

[mittim12]

If the replica were on local storage and the linked clones were on shared storage you could still VMotion around the pool. Here is a great blog post explaining the storage tiering. http://myvirtualcloud.net/?p=1137

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[WillUsher]

Mittim,

I ran across that blog post when I was tryting to figure out where the deltas are located, but as far as I could tell it was not clear from that blog where the delta's were kept.

I understand that if the delta's were on shared storage than vMotion would indeed work, but that seems to somewhat lessen the point of the local storage.

Per the VMware document, the SSD will handle the heavy read and WRITE workload. If only the replica were on local storage, then there would be virtually no write workload on the ssd.

I think you're right in that it may make sense to only have the replicas on local storage, as that would lessen the read workload on the SAN, thus freeing it up for more I/O for the deltas. It would also allow other VMware features such as DRS/vMotion and HA.

[mittim12]

Well you don't have to point them on the local disk. The point of the tiering is to give you the flexibilty to put them in whatever location works best for your environment.

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[WillUsher]

I understand that I don't have to do any of that, but I was wondering what VMware was doing with their particular reference architecture.

Also, does anyone know for sure whether it's a valid configuration either way:

• Running just the replicas on local storage and the deltas on shared storage

• Running both on local storage

Thanks.

[WillUsher]

For anyone wondering; I set it up in my lab, and you are able to set the location for replica's, delta's, and persistent disks each independently.

I assume that means the VMware case study did the following:

Replicas --> Local SSD

Delta's ---> Fast shared storage

Persistent (profile) --> Slow (sata) storage