Il 13-09-2017 10:15 Zdenek Kabelac ha scritto:
Ohh this is pretty major constrain ;)
Sure :p
Sorry for not explicitly stating that before.
But as pointed out multiple times - with scripting around various
fullness moments of thin-pool - several different actions can be
programmed around,
starting from fstrim, ending with plain erase of unneeded snapshot.
(Maybe erasing unneeded files....)
To get most secure application - such app should actually avoid using
page-cache (using direct-io) in such case you are always guaranteed
to get exact error at the exact time (i.e. even without journaled
mounting option for ext4....)
True, but pagecache exists for a reason. Anyway, this is not anything
you can "fix" in device mapper/lvm, I 100% agree with that.
Partially this might get solved in 'some' cases with fully provisioned
thinLVs within thin-pool...
What comes to my mind as possible supporting solution is -
adding possible enhancement on LVM2 side could be 'forcible' removal
of running volumes (aka lvm2 equivalent of 'dmsetup remove --force')
ATM lvm2 prevents you to remove 'running/mounted' volumes.
I can well imagine LVM will let you forcible replace such LV with
error target - so instead of thinLV - you will have single 'error'
target snapshot - which could be possibly even auto-cleaned once the
volume use-count drops bellow 0 (lvmpolld/dmeventd monitoring
whatever...)
(Of course - we are not solving what happens to application
using/running out of such error target - hopefully something not
completely bad....)
This way - you get very 'powerful' weapon to be used in those
'scriplets'
so you can drop uneeded volumes ANYTIME you need to and reclaim its
resources...
This would be *really* great. I played with dm-setup remove/error target
and, while working, it often freezed LVM.
An integrated forced volume removal/swith to error target would be
great.
Thank.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
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