On a Qsan NAS a volume with thin-provisioning enabled, the size option of the volume does NOT grey out like a thin-provisioned file system. This is because for a SAN volume presented to a host, a fixed volume size information is always required and cannot be changing dynamically. 
For a file system with thin-provisioning enabled, the quota and reservation space of the file system from the pool no longer exists. User may notice the file system size option greys out while configuring the file system property or creating a new file system. The thin-provisioning option can be enabled and disabled anytime after a file system is created. 
Thin-provisioning provides great flexibility in free space management, which allows the user to create a file-system with dynamic quota or a volume with capacity prevision possbility.
The data written before the new RAID set is added will be kept in orginal place. Any data modified or written in after the new RAID set is added will be distributed evenly (handled by ZFS algorithm) into the RAID sets based on the portion of free space available from each.
In theory there is no limitation on the number of pools you're allowed to create on a Qsan NAS. However since each pool must contain at least one disk, so the maximum number of pools allowed is equal to the maximum numbers of disks allowed on the system.
By ZFS design, you may only expand the pool capacity by adding additional "RAID sets" in the pool. Browse to the pool options and select "expand" to select free disks for creating an additional RAID set in the pool to expand the pool space.
You cannot expand the existing RAID set in a pool to include more member disks nor migrate the RAID set to a different RAID level. 
Yes, you may create a pool using disks across the JBOD but it is suggested that each RAIDset inside a pool only resides in a single chassis. 
By doing a scrub the pool automatically checks through the ZFS tree structure and verifies all the checksums. You may do this periodically to ensure that the file-integrity is in good status, though the ZFS would also checks the data integrity while the data blocks are being accessed.
No, if a disk belongs to a pool that's been imported an online, the disk cannot be forced free. The disk types allowed for setting free are spare disks and disks in reserved status.
When an encrypted pool is created, a private key for decrypting the pool is automatically generated and stored in the system. When the pool has to be removed and installed on another zfs based Qsan NAS system, upon installation and importing the pool.