About:
-I've read the threads about zfs and databases. Still I'm not 100%
convenienced about read performance. Doesn't the fragmentation of the
large database files (because of the concept of COW) impact
read-performance?
I do need to get back to this thread. The way I am currently
looking at this is this:
ZFS will perform great at doing the transaction
component (say the small (8K) O_DSYNC writes)
because the ZIL will aggregate them in fewer larger
I/Os and the block allocation will stream them to the
surface.
On the other hand, read streaming will require a
good prefetch code (under review) to get the read
performance we want.
If the requirements balances random writes and read
streaming, then ZFS should be right there with the best
FS. If the critical requirement focuses exclusively on read
streaming a file that was written randomly and, in addition,
the number of spindles is limited then that is not the
sweetspot of ZFS. Read performance should still scale with
number of spindles. And, if the load can accomodate a
reorder, to get top per-spindle read-streaming performance,
a cp(1) of the file should do wonders on the layout.
-r
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