Re: 5.1 to 5.5 upgrade causes significant write slowdown (MyISAM + indexes)

[Ben Wallach]

Thanks for your feedback Rick..

As far as the memory/swapping/caching, we are not swapping and we have plenty of memory for both the MySQL key_buffer and the OS caching of MYISAM data. The key buffer can certainly come down, but this is not the issue. The only symptoms are high load and high I/O during writes. Memory is fine.

We conducted another experiment and now things are starting to point to a hardware issue. We installed FC-17+MySQL 5.5 on the original (older) hardware and ran peformance tests against it. The performance was fine (even with the indexes). The MySQL config parameters are set up the same except for the following:
key-buffer old=2GB, new=4GB
inoddodb-buffer old=4GB, new=8GB
inndodb-log-file-size old=256MB, new=512MB
(old RAM=8Gb, new RAM = 16GB)
but again, memory is fine during the writes..

We are going to start looking in the direction of the RAID card and/or Chasis and/or Disks... Hopefully the chip is ok (per your comments)..