Hi Grant, On Fri, Oct 5, 2012 at 10:39 AM, Grant Albitz <[email protected]> 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.
There is no single right answer given the information you've provided. Richard Elling made a spreadsheet to help you find a compromise between bandwidth, IOPS and mean-time-to-data-loss: https://blogs.oracle.com/relling/entry/sample_raidoptimizer_output In addition there are some general rules of thumb for RAIDZ/2/3, like that it may be good to have 2^N+P drives in each stripe. Your alternatives are: 2x9-drive RAIDZ 2x10-drive RAIDZ2 2x11-drive RAIDZ3 4x5-drive RAIDZ 4x6-drive RAIDZ2 = 24 3x7-drive RAIDZ3 So, just going off the rule of thumb (and assuming you want some form of RAIDZ), you'd make a pool that has 4 sets of 6-drive RAIDZ2s. The pool will have the capacity of 16 drives, and the IOPS/bandwidth of a 4-way stripe. Assuming you have the CPU power to keep up with RAIDZ parity calculations, I don't think you can come up with a RAID10 configuration that would offer comparable iops/bandwidth to the 4-way-RAIDZ2. If you have some time before the machine needs to be "in-production", you can try benchmarking a few of the configurations that you think might offer an acceptable MTTDL. Jan _______________________________________________ OpenIndiana-discuss mailing list [email protected] http://openindiana.org/mailman/listinfo/openindiana-discuss
