Hi, perhaps due IOs from the journal? You can test with iostat (like "iostat -dm 5 sdg").
on debian iostat is in the package sysstat. Udo Am 28.04.2014 07:38, schrieb Indra Pramana: > Hi Craig, > > Good day to you, and thank you for your enquiry. > > As per your suggestion, I have created a 3rd partition on the SSDs and did > the dd test directly into the device, and the result is very slow. > > ==== > root@ceph-osd-08:/mnt# dd bs=1M count=128 if=/dev/zero of=/dev/sdg3 > conv=fdatasync oflag=direct > 128+0 records in > 128+0 records out > 134217728 bytes (134 MB) copied, 19.5223 s, 6.9 MB/s > > root@ceph-osd-08:/mnt# dd bs=1M count=128 if=/dev/zero of=/dev/sdf3 > conv=fdatasync oflag=direct > 128+0 records in > 128+0 records out > 134217728 bytes (134 MB) copied, 5.34405 s, 25.1 MB/s > ==== > > I did a test onto another server with exactly similar specification and > similar SSD drive (Seagate SSD 100 GB) but not added into the cluster yet > (thus no load), and the result is fast: > > ==== > root@ceph-osd-09:/home/indra# dd bs=1M count=128 if=/dev/zero of=/dev/sdf1 > conv=fdatasync oflag=direct > 128+0 records in > 128+0 records out > 134217728 bytes (134 MB) copied, 0.742077 s, 181 MB/s > ==== > > Is the Ceph journal load really takes up a lot of the SSD resources? I > don't understand how come the performance can drop significantly. > Especially since the two Ceph journals are only taking the first 20 GB out > of the 100 GB of the SSD total capacity. > > Any advice is greatly appreciated. > > Looking forward to your reply, thank you. > > Cheers. > > > _______________________________________________ ceph-users mailing list [email protected] http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
