[DRBD-user] Pool free report by drbdmanage can't be trust

Julien Escario escario at azylog.net
Mon Jan 25 15:19:57 CET 2016

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hello,
So to continue with my experiments with drbdmanage and thinlv plugin :

drbdmanage 0.91 (same thing seems to happen with 0.50).
storage-plugin = drbdmanage.storage.lvm_thinlv.LvmThinLv

I create a VM with proxmox, 10 GB disk.

Right after, I got this free pool space with drbdmanage list-nodes :
> +------------------------------------------------------------------------------------------------------------+
> | Name | Pool Size | Pool Free |                                                                     | State |
> |------------------------------------------------------------------------------------------------------------|
> | vm4  |    523264 |    521066 |                                                                     |    ok |
> | vm5  |    523264 |    521066 |                                                                     |    ok |
> +------------------------------------------------------------------------------------------------------------+

This is right for vm4 (thin pool is 511 GB) with thin provisionned :
  --- Logical volume ---
  LV Name                drbdthinpool
  LV Size                511.00 GiB
  Allocated pool data    0.00%
  Allocated metadata     0.43%

but can't be considered as right for vm5 :
  --- Logical volume ---
  LV Name                drbdthinpool
  LV Size                511.00 GiB
  Allocated pool data    1.96%
  Allocated metadata     1.43%

AFAIK, drbdmanage should report 511*1024*(1-1.96/100)= 513008 MB free. (almost
my 10GB disk size from 523264 MB).

Now, I created an 5GB disk :
> +------------------------------------------------------------------------------------------------------------+
> | Name | Pool Size | Pool Free |                                                                     | State |
> |------------------------------------------------------------------------------------------------------------|
> | vm4  |    523264 |    521013 |                                                                     |    ok |
> | vm5  |    523264 |    505525 |                                                                     |    ok |
> +------------------------------------------------------------------------------------------------------------+

Wow, so that WAS updated, even before the initial sync finish.

Let's wait for sync to finish and delete this new 5GB disk : still the same report.

So I'm wondering how and when 'pool free' value is calculated. Is it
recalculated only when a new ressource is created ? deleted ?

Is there a way to force it to rescan free space ? (with a dbus command perhaps ?)

That could perhaps be done by a cron job running at defined frequency ?

Regards,
Julien

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