Craig> Does anyone know off the top of their head, or have a reference Craig> for, details or thoughts about NAS (network attached storage) Craig> performance with SSD over spinning rust?
I suspect it's not going to help you much at all... and will certainly cost you a pretty penny. Wouldn't it be cheaper to get some local SSDs and use them as a cache to the backend Drobo instead? The reason I suspect it won't help is both ethernet limits, but also Drobo CPU limits. It's just not designed for IO like this in my book. Craig> I have a Drobo 5N that is currently using 7200rpm drives, and Craig> is on gig-ethernet. I'm looking to squeeze more performance out Craig> of it and am considering replacing drives with either SSD or Craig> 15krpm drives. I'm not concerned about the cost (1Tb drives are Craig> big enough for this array), I simply don't feel like performing Craig> the experiment with one, only to find out the other option Craig> would do better. So your data set fits within 5Tb of storage? Or actually less? Craig> I suspect -- but am not sure how to measure this -- the Craig> constraint is with seeking. The App I'm running on my local Craig> system does a huge amount of read/write seeking all over the Craig> file system. So my hunch is that it's all about the seek Craig> time. That leads me to think that steping up to 15krpm drives, Craig> or to SSD, would be a bit win over the 7200rpm I have now. Are you doing lots of small writes/reads? And it's RAID5, right? Craig> Drobo savy people: this drobo already has the add-on RAM cache installed. Can you give more details on the Drobo configuration and setup? Craig> Sustained i/o: I've done a disk speed test (using Craig> Blackmagicdesign's Disk Speed Test) and I currently get 72+MB Craig> write and 85+MB read from the NAS. If I understand the test Craig> tool, this is a sustained write/read data stream, because the Craig> tool is meant to test for video i/o performance usability. And Craig> if my rusty math is right, gigabit ether converts to 128MB/s Craig> absolute ceiling. ...therefore I don't think I have a problem Craig> (nor any room or desire for much improvement) in terms of Craig> sustained i/o. If you're going to do some performance testing, maybe try using the 'fio' tool on Linux to characterize your performance. >From the sound of it, you're happy to spend a few thousand bucks on this. Maybe the answer is to get another drobo or two and some extra network cards and then shard/span the data across multiple devices. If the data isn't critical, or can be easily re-created from a master source, then a RAID0 stripe across disks might work better. And actualy, you'll get better performance by just getting a couple of SAS/SATA PCIe controllers and a bunch of disks to put local to the system. Then share them out via NFS/CIFS to other hosts if need be. Good luck! John P.S. I haven't even talked about how maybe, just maybe, using lvcache might give you a bunch of performance as well. It all depends though. _______________________________________________ Discuss mailing list [email protected] https://lists.lopsa.org/cgi-bin/mailman/listinfo/discuss This list provided by the League of Professional System Administrators http://lopsa.org/
