Increasing extent size and current data

[Holy Cow]

I have an 1.8TB volume that contains an 800GB extent. This is mounted as an NTFS volume on a Windows server and is now nearly full of data.
I want to expand the extent to the use the full 1.8TB, without losing the current data. The best I can tell, this is how to do it:
1. disconnect the connection from Windows
2. Stop the iSCSI service: Services -> Control Services -> iSCSI set to OFF
2. determine the path of the file extent: Services -> iSCSI -> Extents -> View Extents
3. expand this file by one terabyte: truncate -s +1t /mnt/myZFSVolume/myextent
4. set the extent size to 0 to use the existing size of the file (now 1.8TB): Services -> iSCSI -> Extents -> myextent set 'Extent size' to 0.
5. start the iSCSI service and allow Windows connection
6. Windows Disk Management should mount the original drive and show the the added space as Unallocated. Run Extend Volume to add the new space.

Is this how it should work? Or am I in danger of losing existing data?
Thanks!
(FreeNas build: FreeNAS-9.1.1-RELEASE-x64 (a752d35))

 

[cyberjock]

Few things:

1. iscsi extents will take up more space than you allocate due to block size, checksums, etc.
2. iscsi extents are kept at a reasonable performance when the pool is not filled more than about 50%.
3. zpools themselves shouldn't normally be filled past 80%, and should *never* be filled past 90%.

zfs is a COW file system so you can't fill the pool 100% full or you'll basically lose the pool.

All this being said, you shouldn't be going past about 1TB of data for your total pool if you want iscsi to be well performing. And you shouldn't let the pool go past 80% as a regular course of business for the sake of zfs. So the actual amount of space you should add for a 1.8TB pool is only about 100GB.

The FreeNAS documentation provides the instructions for expanding an iSCSI LUN. So follow those instructions and you can't go wrong.