Ceph settings
In earlier chapters, we discussed the hundreds of internal settings that may be tweaked to optimize Ceph performance or adapt to local needs. The vast majority of these are eldritch and arcane; you're likely to shoot yourself in the foot by tweaking them. In this section we will discuss a number that are conceptually accessible and which have clear benefits.
max_open_files
Earlier in this chapter, we discussed Ceph daemons' thirst for threads. On busy systems they can also run out of file handles. The proper way to increase this limit varies by operating system and Ceph release. Suggested values are a minimum of 131072, and potentially as high as 524288 on dense, busy servers. Recent versions of Ceph allow one to set this in ceph.conf and will raise it on your behalf. Yes, this an OS setting, but Ceph can manage it for us now:
[global] max_open_files = 131072
If your system has /etc/init/ceph-osd.conf, you may raise the value, which may be as low as 32768 there. On other systems...
