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On 2014/9/24 12:10, Brassow Jonathan wrote:<br>
<blockquote
cite="mid:6FC8490A-55CA-454E-83FE-061A33FDE8DE@redhat.com"
type="cite">On Sep 22, 2014, at 7:35 AM, Romu wrote:
<div><br class="Apple-interchange-newline">
<blockquote type="cite"><span class="Apple-style-span"
style="border-collapse: separate; font-family: Helvetica;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: 2; text-align: -webkit-auto; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-border-horizontal-spacing: 0px;
-webkit-border-vertical-spacing: 0px;
-webkit-text-decorations-in-effect: none;
-webkit-text-size-adjust: auto; -webkit-text-stroke-width:
0px; font-size: medium; ">I tried the following command to
set up my era target but the command immediately panics the
system and the system reboots.
<div><br>
</div>
<div># dmsetup create MyEra --table "0 41941903 era
/dev/mapper/VG-CacheDataLV_cmeta /dev/mapper/VG-OriginLV
4096"<br>
</div>
<div><br>
</div>
<div>The metadata dev and the origin dev are all part of a
LVM cache LV. VG-CacheDataLV_cmeta is the cache metadata
LV on the smaller and faster device, VG-OriginLV is the
origin LV on the faster and slower device, 41941903 is the
total sector number of the device of OriginLV (the LV
takes 100% space of the device), 4096 is the block size of
OriginLV, I have run 'mkfs.ext4 /dev/mapper/VG-OriginLV'
before running the dmsetup command.<br>
</div>
<div><br>
</div>
<div>Below is the message in /var/log/messages after running
the dmsetup comnmand:</div>
<div><br>
</div>
<div>kernel: device-mapper: era: sb_check failed: magic
1623043: wanted 2126579579<br>
</div>
<div>
<div>kernel: device-mapper: block manager: superblock
validator check failed for block 0</div>
<div>kernel: device-mapper: era: couldn't read_lock
superblock</div>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Any idea?</div>
</span><br class="Apple-interchange-newline">
</blockquote>
</div>
<br>
<div>Sorry, I haven't used dm-era yet. However, it does appear
that you are perhaps specifying the wrong devices when creating
the era device? Looks like you might be allowing the era target
and the cache target to use the same metadata area at the same
time - causing them to corrupt each other's metadata area?</div>
<div><br>
</div>
<div> brassow</div>
</blockquote>
<br>
I think the dmsetup command to set up an era target should be
something like this:<br>
<br>
<tt><span class="Apple-style-span" style="border-collapse: separate;
font-style: normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: 2;
text-indent: 0px; text-transform: none; white-space: normal;
widows: 2; word-spacing: 0px; font-size: medium;"># dmsetup
create MyEra --table "0 sector_number era metadeta_dev
origin_dev block_size"</span></tt><br>
<br>
My questions:<br>
<br>
1) How to calculate sector_number? According to
<a class="moz-txt-link-freetext" href="https://www.kernel.org/doc/Documentation/device-mapper/era.txt">https://www.kernel.org/doc/Documentation/device-mapper/era.txt</a>, I
guess it should be (4 * nr_blocks) bytes + buffers, but what is
nr_blocks and what is buffers?<br>
2) Any documentation for dmsetup tables?<br>
3) Both my metadata_dev and origin_dev are 10G partitions, is this
all right?<br>
4) My origin_dev is a ext4 filesystem with a block size of 4096, so
the block_size in the command line should also be 4096?<br>
<br>
I tried the following command:<br>
<br>
<tt># dmsetup create MyEra --table "0 160000 era
/dev/mapper/mpathap1 /dev/mapper/mpathbp1 4096"</tt><br>
<br>
It immediately panics the kernel (2.6.32-494.el6.i686) with the
following info in /var/log/messages:<br>
<br>
<tt>Sep 24 22:44:22 localhost kernel: device-mapper: era: sb_check
failed: magic 0: wanted 2126579579</tt><tt><br>
</tt><tt>Sep 24 22:44:22 localhost kernel: device-mapper: block
manager: superblock validator check failed for block 0</tt><tt><br>
</tt><tt>Sep 24 22:44:22 localhost kernel: device-mapper: era:
couldn't read_lock superblock</tt><tt><br>
</tt><tt>Sep 24 22:44:22 localhost kernel: BUG: unable to handle
kernel NULL pointer dereference at 00000008</tt><tt><br>
</tt><tt>Sep 24 22:44:22 localhost kernel: IP: [<f7e9a3c7>]
era_destroy+0x7/0x60 [dm_era]</tt><tt><br>
</tt><tt>Sep 24 22:44:22 localhost kernel: *pdpt = 0000000001945001
*pde = 00000003ff97f067</tt><tt><br>
</tt><tt>Sep 24 22:44:22 localhost kernel: Oops: 0000 [#1] SMP</tt><tt><br>
</tt><tt>Sep 24 22:44:22 localhost kernel: last sysfs file:
/sys/module/dm_mod/initstate</tt><br>
<br>
Thanks<br>
Romu<br>
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