Is anyone using RAID 6 for your servers, SAN, or virtual hosts? I have heard RAID 6 kind of sucks, but have no actual experience with it. I know there aren't any dedicated providers out there setting up RAID 6, so I figured it would be us colo guys if anyone using it. Anyone care to share their thoughts?
raid5 and raid6 are essentially the same in performance terms.
usually the! absolutely! worst! choice! for databases.
will be fastest from 6-12 spindles (except in hitachi ams which are heavily tuned for it)
will be a bit better the larger your write cache is.
will be very much worse if the filesystem (or vm data) is not well aligned on the stripes.
for something more practical - at our my old job we had a few shelfs of raid5 for infrequently used VMs and raid10 for anything else. raid5 was really not great fun, and that was with 3.5GB of write cache.
it might still be ok... if you got a powerful controller it will give you constant performance despite higher latencies. especially if the load won't be insanely high, it might be all OK!
raid6 is interesting because it covers you from double disk failures during a rebuild.
if you have large disks you'll have the problem that a rebuild will take 10+ hours at times and that is a long time of praying to the storage gods.
hope that helped a little.
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As with anything, it depends what you're doing with it.
RAID6 is basically an improvement on RAID5. It can handle two disk failures. With a good controller, it's great for mass storage. We use 16-drive RAID6 arrays on Adaptec 5805Z cards. It has no problems doing 2000+ IOPS of fairly random writes. If we wanted to saturate the sustained bandwidth that it's capable of, we'd need to upgrade the NICs from GigE to 10GigE.
For anything performance-sensitive, such as VMs or databases, I would use RAID10. For mass storage, RAID6 is a good choice.