Data corruption when caching md device that hosts LVM partitions

[dmascord]

Hi guys,

I have been trying to use an SSD device (Samsung 840 pro) as a caching
device on my system, and had used enhanceio to cache /dev/md0 and
/dev/md1. It seems that this was a bad idea, even in read mode, since
it seemed to want to corrupt the underlying ext4 filesystems. I'm not
sure if it was actual corruption, or that fsck thought it was corrupted
due to bad reads, ie, ext4 on lvm -> lvm -> enhanceio -> md0. Anyway,
have since disabled enhanceio caching in that manner, and might create a
cache for each ext4 instead to see if it has less corruption.

My partioning is as follows:

1. /dev/md0 (raid10) as / ext4
2. /dev/md1 (raid10) as LVM Volume Group

Within the LVM volume group, various partitions, such as /usr, /var, /opt, etc.

3. EnhanceIO read-only configured against /dev/md0 and /dev/md1, with appropriately sized partitions on the SSD.

Even though using EnhanceIO gave a performance boost on my desktop system, the corruption worried me that it would start destroying important files rather than dpkg managed files

Any ideas why this configuration would cause corruption ?

Cheers,

Damien