On 13.2.2012, at 21.36, Jan-Frode Myklebust wrote:
Other things that would be interesting to try out (both from latency and disk IO usage point of view):
- maildir_very_dirty_syncs
We already have
$ doveconf maildir_very_dirty_syncs maildir_very_dirty_syncs = yes
but I don't think this gave the advantage I was expecting.. Was expecting this to move most iops to the index-luns, but the maildir luns seems just as busy.
This setting should get rid of almost all readdir() calls. If it doesn't, something's not working right.
- mail_prefetch_count (Linux+maildir only, v2.1+)
Will look into if this works with GPFS when we upgrade to v2.1. It has it's own page cache, so I have no idea if it will respect POSIX_FADV_WILLNEED or if one will need to use it's own API's for hinting:
http://publib.boulder.ibm.com/infocenter/clresctr/vxrx/index.jsp?topic=%2Fco...
I guess if there's an easy way to lookup filename or fd -> blockNumber that wouldn't be difficult to implement with a plugin.