Le 06/08/17 à 12:55, Petter Reinholdtsen a écrit :
[Laurent Bigonville]
The discards commands will also be issued when shrinking or moving a LV
to an other PV, if something is going wrong during these operations, the
data will be lost.

So it's not only when explicitly removing an LV.
Aha.  I did not have the imagination required to consider that such
commands would be issued before the operation was sccessfully completed.
It seemed to me quite obvious that the space would be released only
after the shrink or move was complete, but if that is not the case, it
seem quite unsafe to trust LVM to handle discard commands.

I got hit with a bug while migrating my data from my old non-ssd to ssd drive. In the end I had no data on the SSD (apparently LVM was issuing discards on the destination disk...) and the LV was deleted from the non-ssd one. Hopefully the data were still on the old disk (as it was not supporting DISCARD) so I was able to recover the LV.

While this bug is fixed now, with that kind of experience I can understand why upstream wants to be on the safe side here.

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