Re: Hi! Strange issue with LSR -- bitmaps hadn't been used during 2 of 3 RAIDs resync

[NeilBrown <neilb@suse.de>]

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On Wed, 20 Jun 2012 10:49:32 +0800 Igor M Podlesny <for.poige+lsr@gmail.com>
wrote:

> On 28 May 2012 12:03, Igor M Podlesny <for.poige+lsr@gmail.com> wrote:
> > On 28 May 2012 10:54, NeilBrown <neilb@suse.de> wrote:
> > [...]
> >> The best indicator is total time that it takes (which can probably be
> >> extracted from logs as start and end are logged).  Divide that into size of a
> >> device to get average MB/sec.  If the bitmap was used, that will normally be
> >> much less the best throughput of the device.
> >
> >   That's exactly why I am stating it didn't use WIBs 2 times of 3. It
> > went resyncing from beginning till the end -- I had my finger on its
> > pulse. :)
> >
> >   I can't promise (due to popular "lack of time" disease, yeah), but
> > if I'll get on it using VirtualBox or real environment [Lord forbid
> > :)] once again, I'll let you know, sure.
> 
>    Here it is: http://pastie.org/4118133

This doesn't appear to show the "start to end" that I suggested, just 10% to
30%, but it does suggest that the bitmap isn't speeding things up at all, at
least for that part of the array... That is assuming you are talking about
md124.  I note that md125 doesn't have a bitmap.  Is that what you are
referring to?

The next thing to do would be to look at the bitmap immediately after reboot
to see how many bits are set.  Maybe lots are set for some reason.

> 
>    — 3.4.2-rt10 went suspend ok for 2 times, the 3rd it didn't.
> Reboot, resync, no bitmaps use.
> 
>    And, BTW, it's rather slow in despite of having max. stripe_cache_size set.
> 

A larger stripe cache isn't going to affect resync speed much (I think).
50MB/sec on each drive seems fairly good to me.  What were you expecting?

NeilBrown



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