Il 21-08-2017 01:22 Chris Murphy ha scritto:
Another way is to split the mirror (make one device faulty), and then
fix the remaining drive (now degraded). If that goes well, the 2nd
device can be re-added. Here's a caveat thought: how it resync's will
depend on the write-intent bitmap being present. I have no idea if
write-intent bitmaps on two drives can get out of sync and what the
ensuing behavior is, but I'd like to think md will discover the fixed
drive event count is higher than the re-added one, and if necessary
does a full resync, rather than possibly re-introducing any
corruption.
On the corruption I am replicating (brief SATA power interruptions), the
event count of both drives where identical, and so was the write bitmap
(not always, thought).
To be 100% sure to completly copy from the mirror device, you had to
re-add the corrupted driver as a spare, by using "--add-spare". From the
man page:
"--add-spare
Add a device as a spare. This is similar to --add except that it does
not attempt --re-add first. The device will be added as a spare even if
it looks like it could be an recent member of the array."
Regards.
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Danti Gionatan
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