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Run `fio` on your drives before deploying Ceph:
{{Box|[[File:Warning icon.svg|32px|link=]] {{red|WARNING!}} For those under a rock — fio write test is DESTRUCTIVE. Don’t dare to run it on disks which have containing important data… for example, OSD journals (I’ve seen such cases).}}
* Try to disable drive cache before testing: {{Cmd|hdparm -W 0 /dev/sdX}} (SATA drives), {{Cmd|1=sdparm --set WCE=0 /dev/sdX}} (SAS drives). This is usually ABSOLUTELY required for server SSDs like Micron 5100 or Seagate Nytro (see [[#Drive cache is slowing you down]]) as it increases random write iops ''more than by two magnitudes'' (from 288 iops to 18000 iops!). In some cases it may not improve anything, so try both options -W0 and -W1.
