Date: Wed, 13 Aug 2014 15:40:57 +0200 From: Patrick Proniewski <patpro@patpro.net> To: Martin Simmons <martin@lispworks.com> Cc: freebsd-fs@freebsd.org Subject: Re: zdb -R question Message-ID: <64CCA262-71E9-4688-A725-376DFA681548@patpro.net> In-Reply-To: <201408131020.s7DAKeCl017621@higson.cam.lispworks.com> References: <BEC665FB-4F91-400D-BAA2-67D978C7AC66@patpro.net> <201408131020.s7DAKeCl017621@higson.cam.lispworks.com>
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On 13 août 2014, at 12:20, Martin Simmons wrote:
>> devices ada2 and ada3 are in ZRAID1 mirror.
>
> I think you mean just "mirror"? here. ZRAID1 is not a term used by ZFS -- it
> has RAIDZ1, but that requires at least 3 drives.
Yes, you are right, it's just mirror even though I was thinking about raidz1
>> zpool scrub won't show any error.
>
> If scrub shows no errors then the blocks are not currently used.
thanks for this confirmation.
> For a start, you probably have partitions on the disk so that LBA (from the
> start of the disk) will not be the offset into the ZFS vdev. Secondly, the
> offset passed to zdb -R should be in bytes, whereas the LBA is in sectors.
Before writing to the list I've tried both bytes and sectors/blocks without any positive result.
If I'm not mistaken, 460087328 sectors with a 512 byte size yields to 235564705792 byte offset. So this command should not return "offset must be a multiple of sector size" error:
zdb -R zdata /dev/ada3:235564705792:512
I've used gpart to prepare the drive, so its layout is the following:
# gpart show ada3
=> 34 3907029101 ada3 GPT (1.8T)
34 3907029101 1 freebsd-zfs (1.8T)
I'm quite lost here, with zdb.
> Try using dd on the whole disk, something like
>
> dd if=/dev/ada3 of=/dev/null bs=512 count=1 skip=460087328
>
> Use bs=4096 if your drive has 4096 byte sectors.
dd confirms that the first faulty sector is unreadable:
- faulty sector -
# dd if=/dev/ada3 of=/dev/null bs=512 count=1 skip=460087328
dd: /dev/ada3: Input/output error
0+0 records in
0+0 records out
0 bytes transferred in 9.761358 secs (0 bytes/sec)
- previous sector -
# dd if=/dev/ada3 of=/dev/null bs=512 count=1 skip=460087327
1+0 records in
1+0 records out
512 bytes transferred in 0.035261 secs (14520 bytes/sec)
- next sector -
# dd if=/dev/ada3 of=/dev/null bs=512 count=1 skip=460087329
1+0 records in
1+0 records out
512 bytes transferred in 0.032987 secs (15521 bytes/sec)
thanks,
Pat
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