[Gluster-devel] Disconnections and Corruption Under High Load

Gordan Bobic gordan at bobich.net
Tue Jan 5 12:01:23 UTC 2010

I've noticed a very high incidence of the problem I reported a while 
back, that manifests itself in open files getting corrupted on commit, 
possibly during conditions that involve server disconnections due to 
timeouts (very high disk load). Specifically, I've noticed that my 
.viminfo file got corrupted for the 3rd time today. Since this is root's 
.viminfo, and I'm running glfs as root, I don't have the logs to verify 
the disconnections, though. From what I can tell, a chunk of a dll 
somehow ends up in .viminfo, but I'm not sure which one.

On a different volume, I'm seeing other weirdness under the same high 
disk load conditions (software RAID check/resync on all server nodes). 
This seems to be specifically related to using writebehind+iocache on 
the client-side on one of he servers, exported via unfsd (the one from 
the gluster ftp site). What happens is that the /home volume simply 
seems to disappear underneath unfsd! The attached log indicates a 
glusterfsd crash.

This doesn't happen if I remove the writebehind and io-cache translators.

Other notable things about the setup that might help figure out the 
cause of this:

- The other two servers are idle - they are not serving any requests. 
They are, however, also under the same high disk load.

- writebehind and io-cache is only applied on one server the one behing 
used to export via unfsd. The other servers do not have those 
translators applied. The volume config is attached. It is called 
home-cache.vol, but this is the same file the log file refers to even 
though it is listed there as home.vol.

The problem specifically occurs when servers are undergoing high load of 
the described nature that causes disk latencies to go up massively. I 
have not observed any instances of a similar crash happening without the 
writebehind and io-cache translators.

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