[Pvfs2-developers] Operation cancelled (possibly due to timeout) error

[brain]

* Phil Carns <carns at mcs.anl.gov> [2008 10 17, 10:46]:
> I have two configuration suggestions that you can try.

Hello Phil, hello everybody,

 I followed your suggestions and I verified that adding

 TroveMethod alt-aio

 *and* increasing the ServerJobFlowTimeoutSecs to 300 I don't get any
error, even under heavy load. Now I am wondering if the performances I
get are acceptable or I am just 'hiding' the underlying problem.

 So, I first tried to write to the ext3 slice directly, from every
single host, without using pvfs2, with the following command:

dd if=/dev/zero of="bigfile" bs=4K count=2000000

 It gave me an average of 24 Mb/s with 6 hosts writing at the same time;
with a single host writing the value is 59 Mb/s.

 The same test using pvfs2 resulted in an average 5.7 Mb/s with 5 hosts
writing (on a total of 6 hosts: 1 metadata, 5 I/O), which means 6 times
slower than direct (but parallel) I/O. Is that the "price to pay" :)
for the distributed filesystem?

 If you think that the test I did wasn't meaningful, or need more data
to evaluate it, please just ask, and I'll post all the details.

> One final configuration option that you can try is changing  
> "TroveSyncData no" to "TroveSyncData yes". I would suggest saving that  
> one for last after you have resolved your timeout problem, and then try  
> your benchmark with both settings.

 That's just what I'll do in the next days :)


Thank you very much!