[CentOS] Centos/Linux Disk Caching, might be OT in some ways

Ross Walker rswwalker at gmail.com
Wed Jan 27 14:38:16 UTC 2010


On Jan 27, 2010, at 7:30 AM, Chan Chung Hang Christopher <christopher.chan at bradbury.edu.hk 
 > wrote:

>
> mysql's isam tables have a reputation for surviving just about  
> anything
> and great builtin replication support...
>
> postgresql less so (I suspect due to fake fsync/fsyncdata in the days
> before barriers) but maybe things have improved a lot nowadays.

It has changed a lot since then, where it depended on the OS' fsync  
routine to assure data integrity. Now it uses barriers (where  
supported).

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.

-Ross



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