dm-cache warming

[pullm...@gmail.com]

Hello:

I've been trying to do some performance testing for a client and can't seem to get the dm-cache warmed. The values displayed in the "dmsetup status" command seem too low. I've been trying to use the "raw" devices setup for the cache and NOT use a file system or database. I've tried sequential writes/reads to the devices (ie. dd ) and dividing up the space to be tested and do I/O over a number of segments to try to break any sequential tests. Any ideas as to what I may doing wrong? Do I need to randomize the I/O?

Help...
Dave

[Jorge]

Hello Dave,

I was wondering if you still needed help on how to get the dm-cache warmed. It seems that by doing sequential I/O to the dmcache device you should be fine, though. Just remember that for writes operations to be cached you need to load the dm-cache with the write-back configuration. Also, make sure the you're performing the I/O to the cache device itself (/dev/mapper/foodevice) and not the source device.

If you still need help, let us know.

Regards,

Jorge