Raid 10 vs Raid 5 read performance

[Mattias Jo]

We are using VMware and have a 3PAR storage as primary datastore.
We just bought 2 new ESXi hosts (HPE DL380 Gen10) with local SSD disks (6x400GB) so we can create a local datastore to reduce the load for the 3PAR storage.
Every ESXi host is connected with 2 x 10Gbit/s network.

We are hosting customers SCCM servers so we need great read performance because we are deploying 30-60 clients simultaneously from every VM. Our goal is to have 2-3 VMs stored at the local datastore. When we don’t use the, we move them back to the primary datastore.

The question is, should we use raid 5 or 10 (1+0), or doesn’t it matter in this case? If we use raid 5, it can read from 5 disks simultaneously. Can it read from 3 or 6 disks simultaneously with raid 10?

With Smart Array configuration and raid 5, when we for example choose 512KiB as Strip Size it will be 2.5 MiB Full Stripe Size. With raid 10 the Full Stripe Size will be 1.5 MiB. The explanation for Full Stripe Size is: “The full stripe size is the amount data that the controller can read or write simultaneously on all the drives in the array”.

Obviously we need the best read performance that we can get. Write performance isn’t that important. If a disk fails we just move the VMs to the primary datastore just to be safe. So rebuild time isn’t a big thing either.

So which raid delivers the best read performance with 6 disks?