[gentoo-user] mdadm --create: very low speed on formated disk

[gentoo-user] mdadm --create: very low speed on formated disk

[Jarry]

Hi,

I'm creating /dev/md's for my server with:
mdadm --create --verbose /dev/md0
       --level=1 --raid-devices=2
       /dev/sda1 /dev/sdb1

and I have noticed following thing:

Whenever I create /dev/md0 on a "clean" (not previously
formated) disk, the syncing speed is high (30-40MB/s,
as shown by "cat /proc/mdstat".

But when I try to create raid array on partitions which
have been previously formated (there remained old ext3
formating), syncing speed is not higher than 2-3MB/s
(~15 hours syncing my 160 GB drives!!!).

One more thing: if I delete all partitions, and then write
them back again exactly as they were previously, it doesn't
help. But if I shift all partitions just 1 sector up
(or down), mdadm is again syncing with full speed...

Question: how can I sync with full speed, even if
there are partitions previously used and formated
and I do not want (or can not) move partitions?

Jarry
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