[rrd-users] Disk I/O - use tmpfs

Ofer Inbar cos at aaaaa.org
Wed Mar 26 23:24:32 CET 2008

"Boer, Martin" <martin.boer at atosorigin.com> wrote:
> I've been thinkink about using tmpfs for some time, but as my server
> doesn't have enough memory as it is, I've never been able to try it.
> Doesn't the rsync action use a lot of CPU power and/or I/O itself ?
> Could you show some numbers on the effective performance gain ?

The RRD files are a fixed size.  In normal operation, gmetad writes to
every RRD file constantly (every minute, or more often?).  Doing one
rsync every ten minutes significantly reduces the amount of disk access.

Before I switched to using tmpfs, our gmetad server had its CPU in I/O
wait at 15% or more pretty much all the time.  Whenever it had to do
anything else involving a lot of disk use (like having a nightly
backup) it was extremely slow.

Once I switched to tmpfs, I/O wait went down to under 1% most of the
time, and nightly backups that had taken several hours now took less
than 15 minutes.
  -- Cos

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