Now, I've never setup a journal on a separate disk, I assume you have 4 partitions at 10GB / partition, I noticed in the docs they referred to 10 GB, as a good starter. Would it be better to have 4 partitions @ 10g ea or 4 @20?
I know I'll take a speed hit, but unless I can get my work to buy the drives, they will have to sit with what my personal budget can afford and be willing to donate ;) -Tony On Sun, Mar 1, 2015 at 2:54 PM, Andrei Mikhailovsky <and...@arhont.com> wrote: > I am not sure about the enterprise grade and underprovisioning, but for > the Intel 520s i've got 240gbs (the speeds of 240 is a bit better than > 120s). and i've left 50% underprovisioned. I've got 10GB for journals and I > am using 4 osds per ssd. > > Andrei > > > ------------------------------ > > *From: *"Tony Harris" <neth...@gmail.com> > *To: *"Andrei Mikhailovsky" <and...@arhont.com> > *Cc: *ceph-users@lists.ceph.com, "Christian Balzer" <ch...@gol.com> > *Sent: *Sunday, 1 March, 2015 8:49:56 PM > > *Subject: *Re: [ceph-users] SSD selection > > Ok, any size suggestion? Can I get a 120 and be ok? I see I can get > DCS3500 120GB for within $120/drive so it's possible to get 6 of them... > > -Tony > > On Sun, Mar 1, 2015 at 12:46 PM, Andrei Mikhailovsky <and...@arhont.com> > wrote: > >> >> 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 >> >> >> ------------------------------ >> >> *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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