From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Date: Wed, 13 Sep 2017 10:28:20 +0200 From: Gionatan Danti In-Reply-To: References: <1575245610.821680.1505258554456.ref@mail.yahoo.com> <1575245610.821680.1505258554456@mail.yahoo.com> <052d4c46af896716c0f47132f4ddfb8d@assyoma.it> Message-ID: <738b359eccce111fb8c81733276b9845@assyoma.it> Subject: Re: [linux-lvm] Reserve space for specific thin logical volumes Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Zdenek Kabelac Cc: matthew, LVM general discussion and development 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 GPG public key ID: FF5F32A8