dovecot - May 2021 - Dovecot v2.3.13 reporting (very) incorrect vsize for some maildir folders

> On 20 May 2021, at 14:59, Timo Sirainen <timo at sirainen.com> wrote:
> 
> Well, next step could be to compare individual mail sizes. It would require
writing some kind of a script to do the comparison though.
Hello again,

Apologies, I think dovecot is innocent in all of this.

I noticed that `ls -s` reported a completely different size to `du`, but similar
to what dovecot reports:

# ls -s | head -1
total 14099016
# du
7050436 .

I assume there are some sparseness or block size related shenanigans going on
here instead, causing differences in reported physical usage by `du` (syscall
`newfstatat()`) compared to `ls` (syscall `lstat()`) and dovecot.

The filesystem quota system in Linux, which is what we're migrating from,
apparently uses the same calculation method as `du`, which adds to the
confusion.

- Eirik

> On 20 May 2021, at 15:18, Eirik Rye <rye at trojka.no> wrote:
> 
> I assume there are some sparseness or block size related shenanigans going
on here instead, causing differences in reported physical usage by `du` (syscall
`newfstatat()`) compared to `ls` (syscall `lstat()`) and dovecot.
> 
> The filesystem quota system in Linux, which is what we're migrating
from, apparently uses the same calculation method as `du`, which adds to the
confusion.
Oh, a lot of messages in these folders appear to be hardlinks to the same inodes
(duplicates). Dovecot's vsize-calculation doesn't care that messages are
referencing the same inodes, but `du` and Linux' quota calculation obviously
does.

That explains everything, then. Apologies again for the bother.

- Eirik

On Thu, 20 May 2021, Eirik Rye wrote:
> I noticed that `ls -s` reported a completely different size to `du`, but
similar to what dovecot reports:
>
> # ls -s | head -1
> total 14099016
> # du
> 7050436 .
>
> I assume there are some sparseness or block size related shenanigans
> going on here instead, causing differences in reported physical usage
> by `du` (syscall `newfstatat()`) compared to `ls` (syscall `lstat()`)
> and dovecot.
You'll note the ratio between then is almost exactly 2.  Some utilities
report
space usage in 512-byte block, some in K.  I would hazard a guess that 'ls
-s'
is reporting in blocks, not K.

The man page for my OS 's'ls' states exactly that -- counts are in
blocks.

Joseph Tam <jtam.home at gmail.com>