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From: Liwei <xieliwei@gmail.com>
Date: Wed, 24 Oct 2018 14:36:04 +0800
Message-ID: <CAPE0SYz1YErdNSn0_3MHmyoVXdOr90n1M-nJZ4_TwfzsULzQOg@mail.gmail.com>
Subject: [linux-lvm] Detaching a failed cache pool
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To: LVM general discussion and development <linux-lvm@redhat.com>

Hi list,
    I have an LV with a corrupted cache. Looking at the cmeta using
cache_dump, I get this:

<superblock uuid="" block_size="128" nr_cache_blocks="0" policy=""
hint_width="4">
  <mappings>
metadata contains errors (run cache_check for details).
perhaps you wanted to run with --repair ?

    Running with --repair just produces metadata with no mappings and
hints, which is incorrect too.

    Obviously the metadata volume is corrupted beyond recovery, but I
am okay with that as it is a read-only LV and we are using the cache
for read acceleration. However, there seems to be no way for us to get
out of this state into something usable? I can't seem to remove the
cache from the LV. I've read through the documentation for lvmcache
and can't find any information about this.

    At the moment I can't access the original LV anymore. Whatever I
try to do always results in "Check of pool vg/lv-cache failed
(status:1). Manual repair required!" What am I missing?

Thanks!
Liwei