[OmniOS-discuss] ZFS and Usage-creep

[Richard Elling]

Hi Tim,

On May 12, 2014, at 1:41 PM, Tim Brown <timbrown at muskegonisd.org> wrote:

> I have a question about ZFS usage and how to predictability allocate
> space.  I have scoured the web trying to get a good answer, but have
> yet to find one.
> 
> I am advertising 2TB datastores to our VMware cluster over fiber
> channel using comstar.  I use this command to create the dataset.
> 
> zfs create -V 2047g vmpool01/datastores/ds01

[sidebar discussion]
By default, the volblocksize is 8k. Depending on the zpool configuration
and physical sector size, the allocated space for the data can be larger
than you expect. In general, for pools, we talk about size, free, and
allocated properties. It is often not easy to correlate logical size of
file systems to allocated space in the pool. 

> 
> It all works great but some of my datasets are using far more that the
> 2047g(more than double in one case).  Here are some examples:
> 
> zfs list
> NAME                           USED  AVAIL  REFER  MOUNTPOINT
> ...
> vmpool01                      27.4T  20.7T   469K  /vmpool01
> vmpool01/datastores           27.4T  20.7T   384K  /vmpool01/datastores
> vmpool01/datastores/ds01      3.10T  20.7T  3.10T  -
> vmpool01/datastores/ds02      2.06T  21.4T  1.34T  -
> vmpool01/datastores/ds03      2.69T  20.7T  2.69T  -
> vmpool01/datastores/ds04      2.49T  20.7T  2.49T  -
> vmpool01/datastores/ds05      3.69T  20.7T  3.69T  -
> vmpool01/datastores/ds06      4.67T  20.7T  4.67T  -
> vmpool01/datastores/ds07      2.47T  20.7T  2.47T  -
> vmpool01/datastores/ds08      2.06T  20.8T  1.92T  -
> ...
> 
> Can someone explain this to me or is there a document somewhere that
> can tell me how to predict the usage?  Thanks.

Cleverly hidden in the zfs man page :-). See the discussion on used and
usedby*. Also, a handy option to zfs list is: zfs list -o space
The -o space option breaks out the usedby* to give better visibility.
 -- richard


> 
> - Tim
> -- 
> 
> 
> Tim Brown
> Network System Manager
> Muskegon Area ISD
> http://www.muskegonisd.org
> 231-767-7237
> 
> Always be yourself.
> Unless you can be a pirate.
> Then always be a pirate.
> _______________________________________________
> OmniOS-discuss mailing list
> OmniOS-discuss at lists.omniti.com
> http://lists.omniti.com/mailman/listinfo/omnios-discuss