Re: 10K vs 15k rpm for analytics

"Pierre C" <lists@peufeu.com> wrote:
> Greg Smith <greg@2ndquadrant.com> wrote:

>> I'm curious what you feel those weaknesses are.
>
> Handling lots of small files, especially deleting them, is really
> slow on XFS.
> Databases don't care about that.

I know of at least one exception to that -- when we upgraded and got
a newer version of the kernel where XFS has write barriers on by
default, some database transactions which were creating and dropping
temporary tables in a loop became orders of magnitude slower.  Now,
that was a silly approach to getting the data that was needed and I
helped them rework the transactions, but something which had worked
acceptably suddenly didn't anymore.

Since we have a BBU hardware RAID controller, we can turn off write
barriers safely, at least according to this page:

http://xfs.org/index.php/XFS_FAQ#Q._Should_barriers_be_enabled_with_storage_which_has_a_persistent_write_cache.3F

This reduces the penalty for creating and deleting lots of small
files.

-Kevin