Re: waiting for recovery to complete

[Tim Moore <linux-raid@nsr500.net>]

The recovery daemon adjusts reconstruction speed dynamically according to 
available system resources.

Disk I/O is somewhat slower but works just fine.  You don't have to wait.


Hervé Eychenne wrote:
>  Hi,
> 
> Suppose I'm waiting for a recovery to be completed, and want to run a
> command afterwards (halt, send a mail, or anything else...).
> The most practiacl way I can see is to check /proc/mdstat.
> 
> But what if I want to do that automatically (without bothering looking
> at it manually from time to time)?
> For example, one could do:
> # while cat /proc/mdstat | grep recovery > /dev/null ; do sleep 5 ; done
> 
> But that's quite ugly, as:
> - it's an active polling, and it is time consuming (even if slightly)
> - it may even be unreliable, as I guess one cannot ensure that /proc/mdstat
>   will print the "recovery" string during the (very short, but well...)
>   transition between two partitions to recover
> 
> I think that a passive wait would be much better instead.
> And ideally, we should have a simple and efficient way to let a program
> know if a device is in a clean state (or being recovered), and another
> that would wait until the device is clean (recovery finished).
> 
> So, the while loop could be replaced by something like
>  mdadm --recovery-wait    (for example)
> which would exit only when all pending recoveries have finished, and
> let the script continue.
> That would be much practical, reliable, and cleaner than a loop, don't you
> think?
> 
> How this could be achieved is another question... probably the best
> would be that userspace can select on a file descriptor, or something
> like that (netlink device?)
> What do you think?
> 
>  Hervé
> 

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