I would not use a single ssd for 5 osds. I would recommend the 3-4 osds max per ssd or you will get the bottleneck on the ssd side.
I've had a reasonable experience with Intel 520 ssds (which are not produced anymore). I've found Samsung 840 Pro to be horrible! Otherwise, it seems that everyone here recommends the DC3500 or DC3700 and it has the best wear per $ ratio out of all the drives. Andrei ----- Original Message ----- > From: "Tony Harris" <neth...@gmail.com> > To: "Christian Balzer" <ch...@gol.com> > Cc: ceph-users@lists.ceph.com > Sent: Sunday, 1 March, 2015 4:19:30 PM > Subject: Re: [ceph-users] SSD selection > Well, although I have 7 now per node, you make a good point and I'm > in a position where I can either increase to 8 and split 4/4 and > have 2 ssds, or reduce to 5 and use a single osd per node (the > system is not in production yet). > Do all the DC lines have caps in them or just the DC s line? > -Tony > On Sat, Feb 28, 2015 at 11:21 PM, Christian Balzer < ch...@gol.com > > wrote: > > On Sat, 28 Feb 2015 20:42:35 -0600 Tony Harris wrote: > > > > Hi all, > > > > > > > > I have a small cluster together and it's running fairly well (3 > > > nodes, 21 > > > > osds). I'm looking to improve the write performance a bit though, > > > which > > > > I was hoping that using SSDs for journals would do. But, I was > > > wondering > > > > what people had as recommendations for SSDs to act as journal > > > drives. > > > > If I read the docs on ceph.com correctly, I'll need 2 ssds per > > > node > > > > (with 7 drives in each node, I think the recommendation was 1ssd > > > per 4-5 > > > > drives?) so I'm looking for drives that will work well without > > > breaking > > > > the bank for where I work (I'll probably have to purchase them > > > myself > > > > and donate, so my budget is somewhat small). Any suggestions? I'd > > > > prefer one that can finish its write in a power outage case, the > > > only > > > > one I know of off hand is the intel dcs3700 I think, but at $300 > > > it's > > > > WAY above my affordability range. > > > Firstly, an uneven number of OSDs (HDDs) per node will bite you in > > the > > > proverbial behind down the road when combined with journal SSDs, as > > one of > > > those SSDs will wear our faster than the other. > > > Secondly, how many SSDs you need is basically a trade-off between > > price, > > > performance, endurance and limiting failure impact. > > > I have cluster where I used 4 100GB DC S3700s with 8 HDD OSDs, > > optimizing > > > the write paths and IOPS and failure domain, but not the sequential > > speed > > > or cost. > > > Depending on what your write load is and the expected lifetime of > > this > > > cluster, you might be able to get away with DC S3500s or even > > better > > the > > > new DC S3610s. > > > Keep in mind that buying a cheap, low endurance SSD now might cost > > you > > > more down the road if you have to replace it after a year (TBW/$). > > > All the cheap alternatives to DC level SSDs tend to wear out too > > fast, > > > have no powercaps and tend to have unpredictable (caused by garbage > > > collection) and steadily decreasing performance. > > > Christian > > > -- > > > Christian Balzer Network/Systems Engineer > > > ch...@gol.com Global OnLine Japan/Fusion Communications > > > http://www.gol.com/ > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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