Re: file system and raid performance

[Mark Mielke <mark@xxxxxxxxxxxxxx>]

Andrej Ricnik-Bay wrote:

2008/8/8 Scott Marlowe <scott.marlowe@xxxxxxxxx>:
  

noatime turns off the atime write behaviour.  Or did you already know
that and I missed some weird post where noatime somehow managed to
slow down performance?
    

Scott, I'm quite aware of what noatime does ... you didn't miss a post, but
if you look at Mark's graphs on
http://wiki.postgresql.org/wiki/HP_ProLiant_DL380_G5_Tuning_Guide
they pretty much all indicate that (unless I completely misinterpret the
meaning and purpose of the labels), independent of the file-system,
using noatime slows read/writes down (on average)

That doesn't make sense - if noatime slows things down, then the analysis is probably wrong.

Now, modern Linux distributions default to "relatime" - which will only update access time if the access time is currently less than the update time or something like this. The effect is that modern Linux distributions do not benefit from "noatime" as much as they have in the past. In this case, "noatime" vs default would probably be measuring % noise.

Cheers,
mark

-- 
Mark Mielke <mark@xxxxxxxxx>