Re: 9 second recovery when re-adding a drive that got kicked out?

[NeilBrown <neilb@suse.com>]

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On Tue, Jun 20 2017, Marc MERLIN wrote:

> On Tue, Jun 20, 2017 at 11:27:45AM -0700, Marc MERLIN wrote:
>> On Tue, Jun 06, 2017 at 01:57:27PM +1000, NeilBrown wrote:
>> > Had you run "mdadm --examine-bitmap /dev/sdk1" before the re-add, it
>> > would have told you how many bits were set at that time.
>> > 
>> > That "x/y pages" information never should have appeared in /proc/mdstat
>> > - it is really just of interest to developers.  But it is there now, so
>> > removing it is awkward.
>> 
>> So, I got the problem again, re-added a drive that had just been missing
>> for maybe 2mn, and this time I'm getting a very long (but not full)
>> recovery:
>  
> Mmmh, this is puzzling.
>
> The progress meter was wrong, it recovered in 3mn:
> Jun 20 11:19:28 gargamel kernel: [  916.007017] md: recovery of RAID array md8
> Jun 20 11:22:41 gargamel kernel: [ 1108.395580] md: md8: recovery done.

It is a progress bar - haven't you learned by now that they are *always*
wrong :-)

recovery always reports progress in sectors completed, and estimates
time based on how many sectors were processes in the last 30 seconds,
and how many are left.

With a bitmap based recovery, most sectors are handled very quickly
(instantly?), while some take milliseconds.  That makes the estimate
imprecise.

NeilBrown


>
> Marc
> -- 
> "A mouse is a device used to point at the xterm you want to type in" - A.S.R.
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>                                       .... what McDonalds is to gourmet cooking
> Home page: http://marc.merlins.org/  
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