[tahoe-dev] symlink to storage on a different drive and available space reporting

[David Triendl]

On Tue, Jan 26, 2010 at 09:34:00AM -0700, Jody Harris wrote:
> So, we have several users who are storing the Tahoe shares on a drive other
> than where /home is located.
I have a similar strategy, placing the node data in /var/lib/tahoe and the
shares on a drive mounted at /srv/gridname, and I don't have any problem:

david at mimir:/var/lib/tahoe/testgrid$ ls -l storage
lrwxrwxrwx 1 root root 20 Jan 16 18:18 storage -> /srv/tahoe/testgrid/
david at mimir:/var/lib/tahoe/testgrid$ df -h . storage
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/sda3_crypt
                       14G  2.0G   12G  16% /
/dev/mapper/mimir-testgrid
                      2.0G  699M  1.4G  35% /srv/tahoe/testgrid
david at mimir:/var/lib/tahoe/testgrid$ wget -O - -q http://mimir:3567/storage | grep -A 1 "free (r"
    <tr><td>Disk space free (root):</td>
        <td>1.40 GB</td>

As you can see, the only difference is, that I link storage/ to a different
location, while you link storage/shares. A look at the code
(src/allmydata/storage/server.py) confirms it: There are two directories, one
called the "storedir" (storage/), which the statvfs-call is called for, and the
"sharedir" (storage/shares) which holds the actual shares.

As you can see, the fix is easy: (src/allmydata/storage/server.py, around line
151) replace "disk_avail = self.stat_disk(self.storedir)" with "disk_avail =
self.stat_disk(self.sharedir)", or change the symlink to link storage/ instead
of storage/shares/.

Cheers,
David


> 
> Our strategy at this point is to simply delete the .tahoe/storage/shares
> directory and create a symlink to the desired storage location.
> 
> This results in the available space reported as something completely
> unrelated to reality.
> 
> Obviously, this is the wrong strategy. What does the tahoe-dev team
> recommend?
> 
> thanks,
> Jody
> ----
> - Think carefully.
> - Contra mundum - "Against the world" (St. Athanasius)
> - Credo ut intelliga - "I believe that I may know" (St. Augustin of Hippo)

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