[dm-devel] dmcache RAID1 bug?

[Mike Snitzer]

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 ?

> -- /dev/sda
> -- /dev/sdb
> -- /dev/sdc
> -- /dev/sdd
> 
> Faststorage: RAID1 (mdadm) with 4 SSDs
> - /dev/md/raid1_4hdds

And /dev/md/raid1_4ssds here?

> -- /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
> 
> 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?