Unable to understand the numbers showing up in the Volume Manager

[venkavis]

I have a 3 TB disk (running on 8.3) and I created one ZPOOL and then underneath that created many data sets. I have backed up each data set separately in an external drive so havent configured any RAID.

When I look at volume manager the numbers dont add up. I recall during inital setup the there was no option to specify how much the ZPOOL is bcos I assume that the entire disk is allocated to the ZPOOL.

Please have a look at the below config and tell me how to intepret. My understanding is the disk is organized as DISK-> ZFS VOLUME -> ZFS DATASETS

 

[joeschmuck]

The problem is you are likely expecting ZFS to be understandable. It isn't easily understandable at all. Do a search on the internet for ZFS POOL SIZE, or something like that. Should take you a while but you will find a few things to read about ZFS overhead and pools, etc... You can look at this thread for some insight about the overhead. http://forums.freenas.org/showthread.php?10047-Loss-of-disk-space-disk-size-reduced

 

[gmontalvo]

I have a 3 TB disk (running on 8.3) and I created one ZPOOL and then underneath that created many data sets. I have backed up each data set separately in an external drive so havent configured any RAID.

When I look at volume manager the numbers dont add up. I recall during inital setup the there was no option to specify how much the ZPOOL is bcos I assume that the entire disk is allocated to the ZPOOL.

Please have a look at the below config and tell me how to intepret. My understanding is the disk is organized as DISK-> ZFS VOLUME -> ZFS DATASETS

View attachment 1575

Each dataset can be thought of as a logical drive. Hopefully the attached graphic provides a simple explanation.

To determine the size of the data set, the size within the yellow box plus the size of the blue box will equal the green box. Because "available" may be shared among other datasets (if there is no quota), this value will change - even if you've not copied anything to the dataset.

To determine the size of the entire pool, add up all of the "used" fields (red box) and then add to it "available" (purple box) from a dataset that does not have a quota set.

The percentages are simply "used" divided by "size".

I hope this information helps you to understand this display.