Bug#592149: Fwd: mdadm

[martin f krafft]

also sprach Florian Heigl <florian.heigl at gmail.com> [2010.08.07.2201 +0200]:
> mdadm came with a cronjob that does a periodic check of the configured arrays.
> this check doesn't limit it's bandwidth or priority and basically it is a DOS
> of the system for the runtime. ping will still work, but even ssh login might
> be delayed beyond the standard timeouts.
> 
> the situation is worse with vm's running on top of the affected (host) system.

In my experience, this has never been a problem. But you are not the
first to complain…

> once i tracked down the issue i was able to completely resolve it by changing
> the severity class of the scan to "idle". it continued without very much of a
> slowdown, but the system was perfectly snappy.

Which PID did you iorenice?

> it should be possible to call the verify/resync using ionice to save the hassle
> of tracking the pid.

The verify call is just a write() to the /proc filesystem, the rest
is handled by the kernel. Therefore, iorenice isn't really trivial,
but if there was a single PID to be associated with the verification
run, which I can automatically determine without error, it would be
*much* preferable over the solution suggested in #508123.

Cheers,

-- 
 .''`.   martin f. krafft <madduck at d.o>      Related projects:
: :'  :  proud Debian developer               http://debiansystem.info
`. `'`   http://people.debian.org/~madduck    http://vcs-pkg.org
  `-  Debian - when you have better things to do than fixing systems
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