Hi,
No worries about the typo. I ran iostat -x -m 2 for a few minutes and I
get:
- 0-500KB/s 70% of the time
- 1-2MB/s 20% of the time
- 3-4MB/s 10% of the time.
It never went beyond 4MB/s write speed. But I guess none of this
qualifies as a heavy write. Right?
The fio test can be carried out safely on an active production server
just as you gave it?
Thanks!
Andrei
On 2013-04-22 10:51, Tommy Apel wrote:
Stan>
That was exactly what I was trying to show, that you result may vary
depending on data and backing device, as far as the raid1 goes it
doesn't care much for the data beeing passed through it.
Ben>
could you try to run iostat -x 2 for a few minuts just to make sure
there is no other I/O going on the device before running your tests,
and then run the tests with fio instead of dd ?
fio write test > fio --rw=write --filename=testfile --bs=1048576
--size=4294967296 --ioengine=psync --end_fsync=1 --invalidate=1
--direct=1 --name=writeperftest
/Tommy
2013/4/22 Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>:
On 4/21/2013 2:56 PM, Tommy Apel wrote:
Calm the f. down, I was just handing over some information, sorry
your
day was ruined mr. high and mighty, use the info for whatever you
want
to but flaming me is't going to help anyone.
Your tantrum aside, the Intel 330, as well as all current Intel SSDs,
uses the SandForce 2281 controller. The SF2xxx series' write
performance is limited by the compressibility of the data. What
you're
doing below is simply showcasing the write bandwidth limitation of
the
SF2xxx controllers with incompressible data.
This is not relevant to md. And it's not relevant to Andrei. It
turns
out that the Samsung 840 SSDs have consistent throughput because they
don't rely on compression.
--
Stan
2013/4/21 Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>:
On 4/21/2013 7:23 AM, Tommy Apel wrote:
Hello, FYI I'm getting ~68MB/s on two intel330 in RAID1 aswell on
vanilla 3.8.8 and 3.9.0-rc3 when writing random data and ~236MB/s
writing from /dev/zero
mdadm -C /dev/md0 -l 1 -n 2 --assume-clean --force --run /dev/sdb
/dev/sdc
openssl enc -aes-128-ctr -pass pass:"$(dd if=/dev/urandom bs=128
count=1 2>/dev/null | base64)" -nosalt < /dev/zero | pv -pterb >
/run/fill ~1.06GB/s
What's the purpose of all of this? Surely not simply to create
random
data, which is accomplished much more easily. Are you sand bagging
us
here with a known bug, or simply trying to show off your mad
skillz?
Either way this is entirely unnecessary for troubleshooting an IO
performance issue. dd doesn't (shouldn't) care if the bits are
random
or not, though the Intel SSD controller might, as well as other
layers
you may have in your IO stack. Keep it simple so we can isolate
one
layer at a time.
dd if=/run/fill of=/dev/null bs=1M count=1024 iflag=fullblock
~5.7GB/s
dd if=/run/fill of=/dev/md0 bs=1M count=1024 oflag=direct ~68MB/s
dd if=/dev/zero of=/dev/md0 bs=1M count=1024 oflag=direct ~236MB/s
Noting the above, it's interesting that you omitted this test
dd if=/run/fill of=/dev/sdb bs=1M count=1024 oflag=direct
preventing an apples to apples comparison between raw SSD device
and
md/RAID1 performance with your uber random file as input.
--
Stan
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