On Jan 27, 2010, at 10:20 AM, Noob Centos Admin centos.admin@gmail.com wrote:
Hi,
On 1/27/10, Ross Walker rswwalker@gmail.com wrote:
But if your doing mysql on top of LVM your basically doing the same, cause LVM (other then current kernels) doesn't support barriers.
Still if you have a battery backed write-caching controller that negates the fsync risk, LVM or not, mysql or postgresql.
This is a bit of a surpise. Am I understanding correctly that running postgresql or mysql on top of LVM negates any data reliability measures the DBMS might have in the event of an unexpected shutdown?
I have several servers configured to run LVM on top of MD1 for the convenience of being able to add more space to a volume in the future. I didn't realize this was a reliability risk. :(
Sorry to be the bearer of bad news, but on top of LVM on CentOS/RHEL the best assurance your going to get is fsync(), meaning the data is out of the kernel, but probably still on disk write cache. Make sure you have a good UPS setup, so the disks can flush after main power loss.
-Ross