This was the first forum I found that looked like a relatively general ZFS forum.
I've scoured the Internet before I decided to post this question, so I'm sorry if this is a ZFS noob kind of thing to ask.
I've constructed a 9 disk raid from a set of identical model 6 TB hard drives (Western Digital RED). I've put this into a RaidZ3 configuration, leaving me with 6 disks available for storage (Note: I realize optimally that it should be 2^n + parity, or in other words it should be an 11 disk system, 8 for storage and 3 for parity, but with the computer tower I have and the current arrangement of hard ware inside combined with other requirements, this is the best I can do right now).
My problem is the available space seems around 3TB short of what I'd expect.
See zpool status and zfs list output:
Code: Select all
admin@box:~$ sudo zfs list
NAME USED AVAIL REFER MOUNTPOINT
tank 3.95T 25.7T 236K /mnt/tank
tank/public 3.95T 16.1T 3.95T /mnt/tank/public
tank/backup 236K 4.00T 236K /mnt/tank/backup
admin@box:~$ sudo zpool list
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
tank 49T 6.41T 42.6T - 8% 13% 1.00x ONLINE -
admin@box:~$ sudo zpool status
pool: tank
state: ONLINE
scan: none requested
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
raidz3-0 ONLINE 0 0 0
wwn-0x50014ee20bc64dd3 ONLINE 0 0 0
wwn-0x50014ee20bc9017a ONLINE 0 0 0
wwn-0x50014ee20bc9598d ONLINE 0 0 0
wwn-0x50014ee2611b5bf8 ONLINE 0 0 0
wwn-0x50014ee2611b62fc ONLINE 0 0 0
wwn-0x50014ee2611e0e13 ONLINE 0 0 0
wwn-0x50014ee2611e1948 ONLINE 0 0 0
wwn-0x50014ee2b6715238 ONLINE 0 0 0
wwn-0x50014ee2b6715691 ONLINE 0 0 0
errors: No known data errors
Adding up USED + AVAIL gives: 3.95T + 25.7T = 29.65T. I understand the disk size is listed as 6 * 10^12 bytes on the drive label, yielding approximately 5.46T (5 * 2^40, or 5.46 TebiBytes) bytes per disk. Or multiplied by the 6 disks available for storage, should give about 32.74T of space, not 29.65T. This is a difference of around 3.09T, or more than half of the 5.46T on one disk. I also understand there is always overhead with any file system, but this seems to be an excessive amount, nearly 10% of the expected capacity. Where did this extra space go?
Also, an interesting this to point out: The SIZE in "zpool list" gives 49T, which if you do the calculation of 9 disks * 5.46 T per disk yields 49.11T, or 49T rounded. That seems to actually be correct. Any advice would be great, and thanks in advance.
