Hi Chir, Please fidn my answer below in blue On Thu, Feb 12, 2015 at 12:42 PM, Chris Hoy Poy <ch...@gopc.net> wrote:
> Hi Sumit, > > A couple questions: > > What brand/model SSD? > samsung 480G SSD(PM853T) having random write 90K IOPS (4K, 368MBps) > > What brand/model HDD? > 64GB memory, 300GB SAS HDD (seagate), 10Gb nic > > Also how they are connected to controller/motherboard? Are they sharing a > bus (ie SATA expander)? > no , They are connected with local Bus not the SATA expander. > > RAM? > *64GB * > > Also look at the output of "iostat -x" or similiar, are the SSDs hitting > 100% utilisation? > *No, SSD was hitting 2000 iops only. * > > I suspect that the 5:1 ratio of HDDs to SDDs is not ideal, you now have 5x > the write IO trying to fit into a single SSD. > * I have not seen any documented reference to calculate the ratio. Could you suggest one. Here I want to mention that results for 1024K write improve a lot. Problem is with 1024K read and 4k write .* *SSD journal 810 IOPS and 810MBps* *HDD journal 620 IOPS and 620 MBps* > I'll take a punt on it being a SATA connected SSD (most common), 5x ~130 > megabytes/second gets very close to most SATA bus limits. If its a shared > BUS, you possibly hit that limit even earlier (since all that data is now > being written twice out over the bus). > > cheers; > \Chris > > > ------------------------------ > *From: *"Sumit Gaur" <sumitkg...@gmail.com> > *To: *ceph-users@lists.ceph.com > *Sent: *Thursday, 12 February, 2015 9:23:35 AM > *Subject: *[ceph-users] ceph Performance with SSD journal > > > Hi Ceph-Experts, > > Have a small ceph architecture related question > > As blogs and documents suggest that ceph perform much better if we use > journal on SSD. > > I have made the ceph cluster with 30 HDD + 6 SSD for 6 OSD nodes. 5 HDD + > 1 SSD on each node and each SSD have 5 partition for journaling 5 OSDs on > the node. > > Now I ran similar test as I ran for all HDD setup. > > What I saw below two reading goes in wrong direction as expected > > 1) 4K write IOPS are less for SSD setup, though not major difference but > less. > 2) 1024K Read IOPS are less for SSD setup than HDD setup. > > On the other hand 4K read and 1024K write both have much better numbers > for SSD setup. > > Let me know if I am missing some obvious concept. > > Thanks > sumit > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > >
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