below are the results of my tests with the LSI MegaRAID SCSI 320-2
controller on 3.9-release and 4.0-beta (snapshot pulled on Aug 22, 2006).
I tested writing to both a RAID-5 and a RAID-0 logical drive. The
RAID-0 drive consists of a single drive, what I'd call a JBOD. While
the test program was running, I had iostat running, and I noted the
results next to each test. The iostat values moved around a lot, so I
took a figure close to the peak value.
Naturally all the async tests were influenced by the buffer cache to
a certain extent.
I'm a little confused as to why writing sequential blocks with O_SYNC
should be so slow...
Rob Urban
#======================================================
# 3.9
#======================================================
RAID-0 drive:
----------------
write-test:
----------------------
Sync
----------------------
1 proc: 1.7MB/s
iostat: 1.8MB/s
2 procs: 1MB/s and 1MB/s
iostat: 2MB/s
Async
----------------------
1 proc: 8.7MB/s
iostat: 5MB/s
2 procs: 11MB/s and 5.6MB/s
iostat: 4.8MB/s
dd if=/dev/zero of=testfile bs=64k count=4096
----------------------
took 28.26 seconds, bw: 9MB/s
iostat reported: 4.6MB/s
RAID-5 drive:
----------------
write-test:
----------------------
Sync
----------------------
1 proc: 1.1MB/s
iostat: 1.2MB/s
2 procs: 0.7MB/s and 0.7MB/s
iostat: 1.6MB/s
Async
----------------------
1 proc: 10MB/s
iostat: 3.2MB/s
2 procs: 5.2MB/s and 5.2MB/s
iostat: 5MB/s
dd if=/dev/zero of=testfile bs=64k count=4096
----------------------
took 39.1 seconds, bw: 6.5MB/s
iostat reported: 3.3MB/s
#======================================================
# 4.0-beta
#======================================================
RAID-0 drive:
----------------
write-test:
----------------------
Sync
----------------------
1 proc: 1.5MB/s
iostat: 3MB/s
2 procs: 0.76MB/s and 0.76MB/s
iostat: 3.4MB/s
Async
----------------------
1 proc: 15MB/s
iostat: 10MB/s
2 procs: 8.2MB/s and 5.8MB/s
iostat: 10MB/s
dd if=/dev/zero of=testfile bs=64k count=4096
----------------------
took 21.8 seconds, bw: 11.7MB/s
iostat reported: 10MB/s
RAID-5 drive:
----------------
write-test:
----------------------
Sync
----------------------
1 proc: 1.02MB/s
iostat: 2.5MB/s
2 procs: 0.62MB/s and 0.62MB/s
iostat: 2.9MB/s
Async
----------------------
1 proc: 9MB/s
iostat: 6.3MB/s
2 procs: 4.1MB/s and 3.8MB/s
iostat: 6.5MB/s
dd if=/dev/zero of=testfile bs=64k count=4096
----------------------
took 35 seconds, bw: 7.3MB/s
iostat reported: 7MB/s
