Hi Everyone,
It looks like I've got something weird going with zfs performance on a
ramdisk....ZFS is performing not even a 3rd of what UFS is doing.
Short version:
Create 80+ GB ramdisk (ramdiskadm), system has 96GB, so we aren't swapping
Create zpool on it (zpool create ram....)
Change zfs options to turn off checksumming (don't want it or need it), atime,
compression, 4K block size (this is the applications native blocksize) etc.
Run a simple iozone benchmark (seq. write, seq. read, rndm write, rndm read).
Same deal for UFS, replacing the ZFS stuff with newfs stuff and mounting the
UFS forcedirectio (no point in using a buffer cache memory for something that's
already in memory)
Measure IOPs performance using iozone:
iozone -e -i 0 -i 1 -i 2 -n 5120 -O -q 4k -r 4k -s 5g
With the ZFS filesystem I get around:
ZFS
(seq write) 42360 (seq read)31010 (random read)20953
(random write)32525
Not SOO bad, but here's UFS:
UFS (seq
write )42853 (seq read) 100761 (random read) 100471
(random write) 101141
For all tests besides the seq write, UFS utterly destroys ZFS.
I'm curious if anyone has any clever ideas on why this huge disparity in
performance exists. At the end of the day, my application will run on either
filesystem, it just surprises me how much worse ZFS performs in this
(admittedly edge case) scenario.
--M
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