Return
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Title
yum repolist on redhat Linux causes vasd to hang -
Description
Whenever yum repolist is run on certain boxes ssh logins begin to timeout. Also, QAS commands like "vastool info servers" will also hang until the repolist is complete. -
Cause
The problem was caused by heavy io to /var causing long delays on the fdatasync calls that QAS was running frequently. This seems to be due to the very old hardware on these particular machines which couldn't handle the simultaneous IO well.We were also able to reproduce the slowdown by just writing a file to /var using the dd command, so there is nothing specific to yum that was causing issues. -
Resolution
WORKAROUND
We were able to fix the problem by moving the /var/opt/quest directory to another volume and creating a link to it on /var. This allowed QAS to remained unaffected by the high IO from other applications on /var.