On 2017-03-17 15:25, John Marrett wrote:
Peter,
Bad news. That means that probably the disk is damaged and
further issues may happen.
This system has a long history, I have had a dual drive failure in the
past, I managed to recover from that with ddrescue. I've subsequently
copied the contents of the drives to new disks and expanded them. This
corruption probably stems from issues in the past and not from issues
with the current drives.
One quick tip on this particular note, when you replace a drive (or copy
to new larger drives), run:
btrfs device stats -z
To reset the error counters. This way, you can be sure that the
counters count errors for the filesystem as it currently exists without
leftover counts from any previous drive configuration.
Ideally, the tools would reset them when replacing a device on only that
device, but even if they did, that wouldn't help with simply copying the
filesystem to a new disk.
The other aspect to this is scrubbing regularly and monitoring both the
output of scrub and the error counters, so you know _when_ an error
happened, not just that it happened at some point in the past.
Personally, I would suggest checking the error counters at least daily,
possibly more frequently (it's not an expensive operation, and the
sooner you know about issues the better) and scrubbing at least monthly
(I scrub daily on most of my systems, but I don't store a large enough
amount of data for that to have a significant impact on performance).
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