Jeff Ross wrote:
I followed with great interest the recent thread on misc@
http://marc.theaimsgroup.com/?l=openbsd-misc&m=115620585301672&w=2
aboout bad write performance with the MegaRAID 320-2 card, since I was
also experiencing what I perceived to be slow write performance with the
same card.
Unlike Robert Urban, my set up is three sets of RAID 1 drives, using
Hitachi 10K disks. (dmesg follows).
Here are the results of a couple of tests that I ran with an LSI
MegaRAID 320-2X with and without an onboard battery. I'd love to figure
out why I got no significant change with or without a battery.
bsd.mp with battery installed but not connected, write through, adaptive
read, direct I/O:
[EMAIL PROTECTED]:/home/jross $ dd if=/dev/zero of=/backup/test_file bs=64k
count=102400
102400+0 records in
102400+0 records out
6710886400 bytes transferred in 130.387 secs (51468680 bytes/sec)
bsd.mp with battery installed and connected, write back, adaptive read,
direct I/O:
[EMAIL PROTECTED]:/home/jross $ dd if=/dev/zero of=/backup/test_file bs=64k
count=102400
102400+0 records in
102400+0 records out
6710886400 bytes transferred in 132.209 secs (50759331 bytes/sec)
I believe the reason you, as well as everyone else on this list that has
shared results, are getting similar results with write-back vs
write-through is because you are transferring files larger than your
cache, effectively factoring it out. At this point, the cache battery is
immaterial.
Transfers smaller than your cache size will give you a better
comparison, however, the cache is for reads and writes so the results
may vary depending on usage and the caching algorithm.
-pachl
