Curious problem with asynchronous RAID1 rebuild operations

Hi all,

I tried to rebuild/sync two RAID1 arrays at the same time, with strange results.

When a new drive was added into md0, it started to sync fine at
123,000kb/sec. Whilst that was running, I also added a new drive into
md1, and this causes both arrays sync speed to slow down to
20,000kb/sec. I checked the /proc/sys/dev/raid/speed_limit_{min|max}
and these were both set fine.

I removed the drive from md1, and the md0 sync went back to the normal speed.

RAID Setup:
md0 - 2 drives (2TB Western Digital)
md1 - 2 drives (500GB M3 SDD)

So my question is, does anyone know why the sync speed (on all arrays)
slowed down to almost 6-7 times the norm, when two (or more?) sync
operations are taking place?

Thanks
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