Using XFS with delayed logging mount option (requires kernel 2.6.36 or later).
XFS has natively used delayed allocation for quite some time, coalescing
multiple pending writes before pushing them into the buffer cache. This not
only decreases physical IOPS, but it also decreases filesystem fragmentation by
packing more files into each extent. Decreased fragmentation means fewer disk
seeks required per file read, which also decreases physical IOPS. This also
greatly reduces the wasted space typical of small file storage. Works very well
with maildir, but also with the other mail storage formats.
What happens if you pull out the wrong cable in the rack, kernel
lockup/oops, power failure, hot swap disk pulled, or something else
which causes an unexpected loss of a few seconds of written data?
Surely your IOPs are hard limited by the number of fsyncs (and size of
any battery backed ram)?
Ed W
