Jayson Vantuyl wrote:
Tom,
I currently administer a system running a similar but larger setup, so
I may be able to help you.
First, make sure you contact Coraid. They are really good about
helping with this stuff.
Yes, this is another big area that needs to get looked into. Network
block device is so new (at least on Linux) that it requires some
fine-tuning. If folks have working experiences and willing to share, we
would be very happy to learn from them.
-- Wendy
Second, have you looked at /dev/etherd/err? There is usually a lot of
good debugging there.
Third, have you upgraded the firmware in the Coraid and built the
newest AoE driver? These are absolutely critical in getting the best
performance / reliability and generally the plain kernel driver has
fallen behind. They assure me they're working on this and I can vouch
for the fact that this driver is essentially the one in the kernel
with development necessary to make it work--not some sort of vendor
supplied out-of-tree driver.
Finally, make sure you have good switches. I have had a number of
switches that drop a packet here and there. These are death to AoE
performance. Gigabit is generally a must as well.
On Dec 10, 2006, at 2:03 AM, bigendian+gfs@xxxxxxxxx
<mailto:bigendian+gfs@xxxxxxxxx> wrote:
I've just set up a new two-node GFS cluster on a CORAID sr1520
ATA-over-Ethernet. My nodes are each quad dual-core Opteron CPU
systems with 32GB RAM each. The CORAID unit exports a 1.6TB block
device that I have a GFS file system on.
I seem to be having performance issues where certain read system
calls take up to three seconds to complete. My test app is bonnie++,
and the slow-downs appear to be happen in the "Rewriting" portion of
the test, though I'm not sure if this is exclusive. If I watch top
and iostat for the device in question, I see activity on the device,
then long (up to three second) periods of no apparent I/O. During
the periods of no I/O the bonnie++ process is blocked on disk I/O, so
it seems that the system it trying to do something. Network traces
seem to show that the host machine is not waiting on the RAID array,
and the packet following the dead-period seems to always be sent from
the host to the coraid device. Unfortunately, I don't know how to
dig in any deeper to figure out what the problem is.
Below are strace and tcpdump snippets that show what I'm talking
about. Notice the time stamps and the time spent in system calls in
<> brackets after the call. I'm quite far from a GFS expert, so
please let me know if other data would be helpful.
Any help is much appreciated.
Thanks!
--
Jayson Vantuyl
Systems Architect
*Engine Yard*
jvantuyl@xxxxxxxxxxxxxx <mailto:jvantuyl@xxxxxxxxxxxxxx>
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