Hi, Christian Balzer wrote: >> I'm not sure to well understand: the model that I indicated in the link >> above (page 2, model SSG-6027R-OSD040H in the table) already have hotswap >> bays in the back, for OS drives. >> > Yes, but that model is pre-configured: > 2x 2.5" 400GB SSDs, 10x 3.5" 4TB SATA3 HDDs > Rear 2.5" Hot-swap OS drives (mirrored 80GB SSD) > > What model SSDs and HDDs are those anyway? > > Instead you could use the basically same thing: > http://www.supermicro.com.tw/products/system/2U/6028/SSG-6028R-E1CR12L.cfm > > And put 12 HDDs (of your choice) in the front and 2 fast and durable SSDs > for journals (and OS) in the back. Ok, thx for the link. Sorry for this another question but: are they people that use raid 1 software in the journals dedicated SSDs? For instance, put 3 journals of OSD 1, 2, 3 in SSD1 and create a raid 1 software between SSD1 and SSD2 so that, if SSD1 crashes the OSD 1, 2, 3 are always alive. It seems to me that few people use raid 1 software between journal dedicated SSDs, Am I wrong? It could be a good idea to minimize the risk of loosing a set of OSDs when an SSD crashes. Of course, I imagine that I should decrease the journals per SSD ratio in this case. >>> At this level of density, you'd need about 24GHz combined CPU power to >>> fully utilize the IOPS potentioal of a pure HDD based node. >> >> Ok, can I consider that the general rule is ~1Ghz per OSD in HDD (no >> separate journal)? > > Yes, as per the numerous hardware configuration guides. > No separate SSD journal, journal on the same HDD. Ok. >>> The moment you add SSD journals to this picture, that number at _least_ >>> doubles, making it a potentially very power hungry unit. >> >> So, if I understand well, I should estimate ~2Ghz per OSD with journal in >> separate SSD. Is that correct? > > At least. > With a fio like this inside a VM: > --- > fio --size=4G --ioengine=libaio --invalidate=1 --direct=1 --numjobs=1 --rw=randwrite --name=fiojob --blocksize=4K --iodepth=32 > -- > I can make all 8 3.1GHz core on an 8 OSD server with 4 journal SSDs reach > 100% utilization. > > CPU to IOPS ratio is likely to improve as Ceph improves, but this is with > Firefly and I doubt even the just released Hammer would change that very > much. [...] >> Is a HBA/RAID systematically necessary? >> > With the model you cited, yes. All those ports need to be connected up (4 > SATA links per port). > >> Are there some hardware configurations where it could possible to >> consider disks directly connected to the controller of the motherboard? >> > Depends on the motherboard, see the concurrent "Motherboard" thread on > this ML. Ok, thx a lot Christian for all this information and feedbacks. -- François Lafont _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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