[OpenIndiana-discuss] Raid type selection for large # of ssds

[Dan Swartzendruber]

On 10/5/2012 12:39 PM, Grant Albitz wrote:
> I feel bad asking this question because I generally know what raid type to pick.
>
> I am about to configure 24 256gig ssd drives in a ZFS/Comstar deployment. This will serve as the datastore for a vmware deployment. Does anyone know what raid level would be best. I know the workload will determine alot, but obviously there is varying workload across a vmware environment. Since we are talking about ssds I dont see a particular reason to not create 1 big zfs pool, with the exception that I know people generally try to keep the drive count from getting out of control. Raid 10 seems like a waste of space with little benefit in performance in this case. i am leaning towards raid z2 but wanted to get everyones input.
>
> The datastore will host a fileserver, and exchange server for about 50 users. The environment is all 10g and they have solid states in all desktops so essentially that is the reason for such a large SSD deployment for a small # of users.
>
> There seems to be varying opinions, especially when you factor in trying to keep writes low for ssds.
>    
a 24-drive raidz2 is a really bad idea.  you will get one drive IOPs.  
you said raid10 is a waste?  depends on your workload.  keep in mind for 
read-heavy random IOPs, raid10 is extremely good.  If you insist on some 
raidz* flavor, I would do something like 3 8-drive raidz2 vdevs, so you 
get 3 vdevs random IOPs...