[libvirt] directory storage pools reported available space

[Ryan Harper]

* Osier Yang <jyang at redhat.com> [2010-12-03 00:23]:
> ??? 2010???12???03??? 14:00, Ryan Harper ??????:
> >We recently had an issue with not being able to allocate the full
> >capacity of a directory based storage pool.  The reported value via
> >pool-info was larger than what was available to the image creator.
> >
> >Looking at the storage code, in virStorageBackendFileSystemRefresh()
> >we're using statvfs, and reporting back
> >
> >    pool->def->available = ((unsigned long long)sb.f_bfree *
> >                           (unsigned long long)sb.f_bsize);
> >
> >Which is the amount of blocks available, including any root reservation
> >if present on the filesystem.
> >
> >This does't line up with df output , which at least on RHEL5 and 6
> >systems reports the available space from f_bavail, which excludes
> >and reserved space.
> >
> >Is it reasonable to have the available value line up with output from df
> >and not report reserved space?
> >
> It's misleading not to exclude the reserved space, probly it will be
> nicer to report both the actually avaiable spaces and the reserved
> ones.

I argue the opposite.  df doesn't show you the reserved space.  the
first thing someone does to compare the values between libvirt directory
pool and df.

I don't mind reporting both but, I've yet to see a tool to report the
reserved value rather than the non-reserved.


> 
> - Osier
> 
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-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh at us.ibm.com