Keep in mind also if you want to have fail over in the future. We were running a 2nd server and were replicating via DRBD the raid arrays. Expanding this storage is quite hastle, compared to just adding a few osd's.
-----Original Message----- From: Oscar Segarra [mailto:oscar.sega...@gmail.com] Sent: maandag 13 november 2017 15:26 To: Peter Maloney Cc: ceph-users Subject: Re: [ceph-users] HW Raid vs. Multiple OSD Hi Peter, Thanks a lot for your consideration in terms of storage consumption. The other question is considering having one OSDs vs 8 OSDs... 8 OSDs will consume more CPU than 1 OSD (RAID5) ? As I want to share compute and osd in the same box, resources consumed by OSD can be a handicap. Thanks a lot. 2017-11-13 12:59 GMT+01:00 Peter Maloney <peter.malo...@brockmann-consult.de>: Once you've replaced an OSD, you'll see it is quite simple... doing it for a few is not much more work (you've scripted it, right?). I don't see RAID as giving any benefit here at all. It's not tricky...it's perfectly normal operation. Just get used to ceph, and it'll be as normal as replacing a RAID disk. And for performance degradation, maybe it could be better on either... or better on ceph if you don't mind setting the rate to the lowest... but when the QoS functionality is ready, probably ceph will be much better. Also RAID will cost you more for hardware. And raid5 is really bad for IOPS. And ceph already replicates, so you will have 2 layers of redundancy... and ceph does it cluster wide, not just one machine. Using ceph with replication is like all your free space as hot spares... you could lose 2 disks on all your machines, and it can still run (assuming it had time to recover in between, and enough space). And you don't want min_size=1, and if you have 2 layers of redundancy, you'll be tempted to do that probably. But for some workloads, like RBD, ceph doesn't balance out the workload very evenly for a specific client, only many clients at once... raid might help solve that, but I don't see it as worth it. I would just software RAID1 the OS and mons, and mds, not the OSDs. On 11/13/17 12:26, Oscar Segarra wrote: Hi, I'm designing my infraestructure. I want to provide 8TB (8 disks x 1TB each) of data per host just for Microsoft Windows 10 VDI. In each host I will have storage (ceph osd) and compute (on kvm). I'd like to hear your opinion about theese two configurations: 1.- RAID5 with 8 disks (I will have 7TB but for me it is enough) + 1 OSD daemon 2.- 8 OSD daemons I'm a little bit worried that 8 osd daemons can affect performance because all jobs running and scrubbing. Another question is the procedure of a replacement of a failed disk. In case of a big RAID, replacement is direct. In case of many OSDs, the procedure is a little bit tricky. http://ceph.com/geen-categorie/admin-guide-replacing-a-failed-disk-in-a-ceph-cluster/ <http://ceph.com/geen-categorie/admin-guide-replacing-a-failed-disk-in-a-ceph-cluster/> What is your advice? Thanks a lot everybody in advance... _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> -- -------------------------------------------- Peter Maloney Brockmann Consult Max-Planck-Str. 2 21502 Geesthacht Germany Tel: +49 4152 889 300 <tel:+49%204152%20889300> Fax: +49 4152 889 333 <tel:+49%204152%20889333> E-mail: peter.malo...@brockmann-consult.de <mailto:peter.malo...@brockmann-consult.de> Internet: http://www.brockmann-consult.de <http://www.brockmann-consult.de> -------------------------------------------- _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
