[dm-devel] dmcache RAID1 bug?

[Leonardo Santos]

I tested updating my xbox to same production kernel (3.17.2) and the
problem appears now.

The old kernel (ok) is 3.13.0-37.

About updating lvm, I think it should not be, because this time I did not
use them and did creating only through the dmsetup command.

I will continue testing with other kernels.

Can anyone help me?


On Mon, Nov 17, 2014 at 4:14 PM, Leonardo Santos <heiligerstein at gmail.com>
wrote:

> On Mon, Nov 17, 2014 at 12:46 PM, Mike Snitzer <snitzer at redhat.com> wrote:
>
>> On Mon, Nov 17 2014 at  9:24am -0500,
>> Leonardo Santos <heiligerstein at gmail.com> wrote:
>>
>> > I'm working in tests for my msc thesis envolving dm_cache module. I'm
>> > having problems with the following scenario:
>> >
>> > Slowstorage: RAID1 (mdadm) with 4 HDDs;
>> > - /dev/md/raid1_4ssds
>>
>> You mean /dev/md/raid1_4hdds ?
>>
>
> A symlink to raid1 created using 4 ssds.
>
> mdadm --create --verbose /dev/md/raid0_4ssds --raid-devices=4 --force
> --level=1 /dev/sdd /dev/sdc /dev/sdb /dev/sda
>
>
>>
>> > -- /dev/sda
>> > -- /dev/sdb
>> > -- /dev/sdc
>> > -- /dev/sdd
>> >
>> > Faststorage: RAID1 (mdadm) with 4 SSDs
>> > - /dev/md/raid1_4hdds
>>
>> And /dev/md/raid1_4ssds here?
>>
>
> mdadm --create --verbose /dev/md/raid0_4hdds --raid-devices=4 --force
> --level=1  /dev/sdh /dev/sdg /dev/sdf /dev/sde
>
>
>>
>> > -- /dev/sde
>> > -- /dev/sdf
>> > -- /dev/sdg
>> > -- /dev/sdh
>> >
>> >
>> > Cachestorage: dm_cache envolving both devices
>> > - /dev/mapper/dmcache
>> > -- /dev/md/raid1_4ssds
>> > -- /dev/md/raid1_4hdds
>> >
>>
>
> Commands:
> vgcreate cache /dev/md/raid0_4ssds -y
> lvcreate cache -n metadata -l 5%FREE
> lvcreate cache -n block -l 100%FREE
> dd if=/dev/zero of=/dev/cache/metadata bs=1M count=100
> # 16773120 = blockdev --getsize /dev/md/raid0_4hdds
> dmsetup create dmcache --table '0 16773120 cache /dev/cache/metadata
> /dev/cache/block /dev/md/raid0_4hdds 512 1 writeback default 0'
>
>
>> > Other informations (strange facts):
>> > In RAID0 it's working very well.
>> > In a virtual machine (vbox) it's working as well (in this case disks
>> have
>> > 2GB only for big tests automatization, in production are 160GB SSDs and
>> 2TB
>> > HDDs);
>> >
>> > Have you seen about this error? Syslog is bellow.
>>
>> Never seen this before... have you taken care to zero the dm-cache
>> metadata's superblock (first 512B of the cache metadata device) each
>> time you've reconfigured the cache device?
>>
>> Have you tried using the latest lvm2 to create the dm-cache device?
>>
>
> I've used LVM2 from distribution (debian) and a latest kernel version.
>
> LVM2 latest today is 2.02.112 (I'll try with latest LVM2 version and post
> results).
>
> # lvm version
>   LVM version:     2.02.95(2) (2012-03-06)
>   Library version: 1.02.74 (2012-03-06)
>   Driver version:  4.27.0
>
> # uname -a
> Linux steinhager 3.17.2 #2 SMP Fri Nov 7 12:49:16 BRST 2014 x86_64
> GNU/Linux
>
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