Hi,

I wanted to know how much space is consumed by zfs metadata (including
ZAP, ZIL) on a zpool. Is there any command(zdb maybe) to know that?

Also, how do I estimate space required for metadata in future? Let me
explain with an example of following scenarios:

1. Worst case scenario: creating a new file with exactly 128KB of data
till no space is left on the zpool.
2. Best case scenario: adding a block of exactly 128KB of data to
existing file till no space is left on the zpool.

I created a zpool of 128MB size. It looks like zfs reserves some space
upfront as, only 123M were available out of 128M (see output of zpool
command). Is remaining 5MB space used for metadata inlcuding ZIL?
Also, zpool output shows 110K used, what is that for? Furthermore, zfs
seems to return ENOSPC when just 32M is remaining in the zpool. Is
there a static check in the code for last 32M?

[EMAIL PROTECTED]:/# zpool list
NAME                    SIZE    USED   AVAIL    CAP  HEALTH     ALTROOT
zp                      123M    110K    123M     0%  ONLINE     -

For worst case, I managed to create 726 files of 128KB each (total
~91MB) which matches with 123M-32M space calculation. Similarly, for
the best case scenario, I managed to write 727 blocks of 128KB each
(total ~91MB). Now how do I find out, how much space was used to store
metadata for 726 files in worst case and 727 blocks in best case?
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