It depends
and without knowing a bit about the makeup of the array or the disks each CPG points to I can only point you in the right direction.
Total 26,784 GiB - Allocated 14,293 GiB = Free 12,491 GB which is RAW capacity
However this free number is spread over 3 CPG's and it will depend on the parity overheads and whether the CPG's address the same or different disks as to how much you have available in each.
Note CPG space is expressed as usable (logical) based on the properties of the CPG not the RAW number.
CPG1 (RAID1):
Used 3,400 GiB (how much space you have written)
Allocated 3,445 GiB (how much space has been reserved by the CPG)
Free 46 GiB (how much space is available before the CPG grows again to accomodate new writes)
Estimated usable free space 6,245 GiB (this is usable space available for the CPG to grow into e.g. 6,245GB Usable * 2 for mirroring = 12,491GB Raw above)
CPG2(RAID5):
Used 2,015 GiB (Written)
Allocated 2,030 GiB (Reserved)
Free 15 GiB (Free until next grow)
Estimated usable free space 10,375 GiB (Estimated usable 10,375GB *1.2 for Raid 5(4+1) = 12,451GB Raw)
CPG3(RAID6):
Used 2,304 GiB (Written)
Allocated 2,335 GiB (Reserved)
Free 31 GiB (Free until next grow)
Estimated usable free space 8,298 GiB (Estimated usable 8,298GB usable *1.33 for Raid 6 (4+2) = 11,040GB Raw) - the remainder can possibly be explained by me getting my sums wrong or not being able to complete a full row based on the number of disks and set size being used.
Since the raid 1 raw figure matches your available free space I'd assume these CPG's are all sharing the same disks ? In which case all of the above are correct but it just depends on which one grows at any one time. But in summary you have 12,491GB RAW free of additional unallocated capacity that the system can allocate to any one of the CPG's based on a first come first served basis.
Try running a cli% showpd -c at the CLI and it'll show you the used and free chunklets available per disk, using the above you should be able to calculate the same.
