VSAN design for datastores

[AkkiAus]

HI, I am new with VSAN. I am working for a small company and considering implementing VSAN on 3 node cluster.

I want to set up VSAN such a way that i can store database and production servers on faster drives (15K) and other data on slow drives (7.2K) is there any way i can achieve this in VSAN? As i can see i can only create one vsandatastore (created automatically) and assign disks to disk groups, but no options to store vhdk on selected disk group or may be create 2 vsandatastore (don't know it is possible or not) and configure disk groups on one with faster drives and other with slower.

Can any one please guide me here how can we achieve this? any suggestion will be appreciated.  

[crosdorff]

Vsan does *not* support multiple disk tiers at the moment.

As you have seen only one datastore can be made.

If you size your ssds correct, only a very small part from your iops comes from the magnetic disks.

So it should be save to go with 10k rpm disk or even with 7.2k rpm.

Although I don't think it will be a very big price difference in a 3 node cluster.

If you take a look at the vSan ready nodes list available at http://partnerweb.vmware.com/programs/vsan/Virtual%20SAN%20Ready%20Nodes.pdf you can see that for example HP is using 10k disks for all the systems.

[AkkiAus]

Thanks Crosdorff

we have purchased 3 x HP DL380e G8 and have some 9x 600GB 15K drive and 12x 7.2k 4TB drives and 10 x 200GB SSDs. i am planning to allocate 1:3 (ssd:15Kdrive) and 1:2 (ssd:7.2K drive) but still not sure about the IO performance with this config.

I wanted to use all SSDs but VSAN doesn't support all SSDs either. I will test this set up and see how it will go.

[crosdorff · Accepted solution]

Al-tough it is possible to create one group with 1x ssd and 3x 600GB 15k rpm and another group with 1x ssd and 2x 4TB 7200rpm I will strongly advise against it.

There is (currently) no way to force your vm's to use the 'fast' or the 'slow' disk groups.

All the disk groups are aggregated in one big datastore.

Currently it's best practices and recommended to use equal disk groups.

[AkkiAus]

Thanks Crosdorff

I understand that, I will probably buy more 10K drives and big SSD (500GB/1TB) to increase the performance. I will try not to use 7.2K drives along with 10/15K drives.

[eddyccl]

I think you can mix different capacity of drives in a single Disk Group and then use VM storage policies to select which type of disks to use. Correct me if i'm wrong.

[crosdorff]

eddyccl wrote:

I think you can mix different capacity of drives in a single Disk Group and then use VM storage policies to select which type of disks to use. Correct me if i'm wrong.

You are wrong.

It's not possible to use storage policies to select disk types.

It's not recommended to mix disk type and or size within one disk group or one cluster.

[eddyccl]

Oh i see. Yea, I just Google around and found the same answer. Thanks for pointing out