Hi Martin, thanks for your reply :) We already have a separate NVMe SSD pool for cephfs metadata. I agree it's much simpler & more robust not using a separate DB/WAL, but as we have enough money for a 1.6TB SSD for every 6 HDD, so it's tempting to go down that route. If people think a 2.2% DB/WAL is a bad idea, we will definitely have a re-think. Perhaps I'm being greedy for more performance; we have a 250 node HPC cluster, and it would be nice to see how cephfs compares to our beegfs scratch. best regards, Jake On 5/28/19 3:14 PM, Martin Verges wrote: > Hello Jake, > > do you have any latency requirements that you do require the DB/WAL at all? > If not, CephFS with EC on SATA HDD works quite well as long as you have > the metadata on a separate ssd pool. > > -- > Martin Verges > Managing director > > Mobile: +49 174 9335695 > E-Mail: martin.verges@xxxxxxxx <mailto:martin.verges@xxxxxxxx> > Chat: https://t.me/MartinVerges > > croit GmbH, Freseniusstr. 31h, 81247 Munich > CEO: Martin Verges - VAT-ID: DE310638492 > Com. register: Amtsgericht Munich HRB 231263 > > Web: https://croit.io > YouTube: https://goo.gl/PGE1Bx > > > Am Di., 28. Mai 2019 um 15:13 Uhr schrieb Jake Grimmett > <jog@xxxxxxxxxxxxxxxxx <mailto:jog@xxxxxxxxxxxxxxxxx>>: > > Dear All, > > Quick question regarding SSD sizing for a DB/WAL... > > I understand 4% is generally recommended for a DB/WAL. > > Does this 4% continue for "large" 12TB drives, or can we economise and > use a smaller DB/WAL? > > Ideally I'd fit a smaller drive providing a 266GB DB/WAL per 12TB OSD, > rather than 480GB. i.e. 2.2% rather than 4%. > > Will "bad things" happen as the OSD fills with a smaller DB/WAL? > > By the way the cluster will mainly be providing CephFS, fairly large > files, and will use erasure encoding. > > many thanks for any advice, > > Jake > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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