On Aug 12, 0:55, Jim Davis wrote:
Disk manufacturers use metric megabytes...
19disks x 4 x 10 ^ 9Bytes/disk = 7.6 x10 ^ 10 = 76000000KBytes
Which shaves some off the difference. Having said that, most disks are actually 4.x GBytes, so you'll probably see the full 4GBytes useable.
I didn't think there was any FFSishness left in the WAFL - though WAFL metadata evidently requires a fair bit of space, especially if well used.
Have you already deducted the Parity and Hot Spares space?
19disks - 1 Parity - 1 HotSpare = 17 disks for user-data.
17disk x 4 x 10 ^ 9Bytes/disk = 68000000KBytes. Which looks very close to your figure from df...
I didn't think there was any FFSishness left in the WAFL
There is a 10% space reserve in WAFL, just as there is in FFS, except that even the super-user isn't allowed to go over it. (If you want to know why it's there, ask Dave Hitz; I don't remember offhand.)