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? root at unknown:/# 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?