I have a RAID5 array with 4 active devices and two spares. The spares
are normally in sleep mode. I ran a resync with:

echo repair > /sys/devices/virtual/block/md0/md/sync_action

About 20 times (evenly spaced apart) during the resync, the spares
were written to, waking them up. Is that behavior desired? It seems to
me that it's a waste--I don't know why the resync would bother with
the spares.

--Rory
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On 13/04/2011 23:10, Rory Jaffe wrote:
> I have a RAID5 array with 4 active devices and two spares. The spares
> are normally in sleep mode. I ran a resync with:
>
> echo repair> /sys/devices/virtual/block/md0/md/sync_action
>
> About 20 times (evenly spaced apart) during the resync, the spares
> were written to, waking them up. Is that behavior desired? It seems to
> me that it's a waste--I don't know why the resync would bother with
> the spares.
>

This isn't an answer to your question, but I would recommend changing to
a raid 6 with 5 devices and one spare. Raid 6 gives you /much/ better
reliability - you can thing of it as Raid 5 + hot spare with the hot
spare already synchronised.


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On Wed, 13 Apr 2011 14:10:46 -0700 Rory Jaffe <rsjaffe [at] gmail.com> wrote:

> I have a RAID5 array with 4 active devices and two spares. The spares
> are normally in sleep mode. I ran a resync with:
>
> echo repair > /sys/devices/virtual/block/md0/md/sync_action
>
> About 20 times (evenly spaced apart) during the resync, the spares
> were written to, waking them up. Is that behavior desired? It seems to
> me that it's a waste--I don't know why the resync would bother with
> the spares.

Yes, there is room for optimisation there. It really shouldn't write to
those devices. I guess I should try (again) to fix that.

Thanks for the report.

NeilBrown
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