dm-thin: Retrieve physical used/free space in a dm-thin pool

[cmaiolino]

Hi,

Any possibility of adding an API call to retrieve space usage on an dm-thin pool?

Thanks

[vpodzime]

Hi,
we have the bd_lvm_cache_stats() function which is actually just querying DM info. It would be very easy to add a similar function for a generic DM thin pool used outside of an LVM setup. I take it that's your case, @cmaiolino?

[cmaiolino]

Hi,
we have the bd_lvm_cache_stats() function which is actually just querying DM info. It would be very easy to add a similar function for a generic DM thin pool used outside of an LVM setup. I take it that's your case, @cmaiolino?

Heya,

Taking a quick look at what kind of information bd_lvm_cache_stats() returns, if such information can be retrieved from the thin pool itself (not from the volume), it can work. The information I really need is the real pool utilization, so I can check in case overcommitting of a thin volume, how much physical space is being used. Does it make more sense? :P

Cheers

[vpodzime]

OH! I somehow read dm-cache instead of dm-thin, please ignore my previous comment.

In the result of bd_lvm_lvinfo() we have data_percent and metadata_percent, which is the usage info when then function is called on a thin pool (or any other pool, for that matter). However, it only works for LVM thin pools, not generic DM thin pools.

[cmaiolino]

yeah, that's the thing. I can't assume the users of the application I'm writing, will always be using LVM to manage dm-thin, that's why I wanted something to interact directly with device-mapper. Thanks for having a look into it btw :)

…

On Mon, Jun 17, 2019 at 11:01 AM Vratislav Podzimek < ***@***.***> wrote: OH! I somehow read dm-cache instead of dm-thin, please ignore my previous comment. In the result of bd_lvm_lvinfo() <http://storaged.org/libblockdev/libblockdev-LVM.html#bd-lvm-lvinfo> we have data_percent and metadata_percent, which is the usage info when then function is called on a thin pool (or any other pool, for that matter). However, it only works for LVM thin pools, not generic DM thin pools. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#444?email_source=notifications&email_token=AAFMAMVQYBEZCD4L7VXJ2T3P25HINA5CNFSM4HXWPO5KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODX2QRHI#issuecomment-502597789>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAFMAMSLSB5W4VEDO5FRIFDP25HINANCNFSM4HXWPO5A> .

[vpodzime]

I'll take a look at how hard it would be to add some bd_dm_pool_stats() function, hopefully for DM pools in general (to get back to my cache-misleading-path 😄).