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Date:      Wed, 03 Jul 2013 09:53:03 -0500
From:      "Mark Felder" <feld@feld.me>
To:        mxb <mxb@alumni.chalmers.se>, "Daniel Kalchev" <daniel@digsys.bg>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: Slow resilvering with mirrored ZIL
Message-ID:  <op.wzniapoj34t2sn@tech304.office.supranet.net>
In-Reply-To: <51D437E2.4060101@digsys.bg>
References:  <CABBFC07-68C2-4F43-9AFC-920D8C34282E@unixconn.com> <51D42107.1050107@digsys.bg> <2EF46A8C-6908-4160-BF99-EC610B3EA771@alumni.chalmers.se> <51D437E2.4060101@digsys.bg>

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On Wed, 03 Jul 2013 09:40:34 -0500, Daniel Kalchev <daniel@digsys.bg>  
wrote:

>
> What is happening during resilver is reading from the other drives in  
> the vdev and writing to the new drive. You mention four drives so I  
> assume this is an raidz? Is it possible that the old drives and the  
> zpool vdev(s) are 512byte sector size and the new drive is 4k sector  
> size? If so, you might experience severe slowdown. The only way to fix  
> this situation is to recreate the zpool -- copy data out of the pool,  
> create the pool with 4k alignment for vdevs and copy data back.

This might be what he's experiencing -- I ran into this recently when I  
knowingly put a 4K drive into a server that used 512b sectors in the  
zpool. It was an emergency as we ran out of 512b 2TB spares. As soon as we  
got a proper spare I did replace the drive and performance went back to  
normal and the resilver was extremely fast too.



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