Skip to content

Commit

Permalink
RAIDZ.rst: add note about usable space (#477)
Browse files Browse the repository at this point in the history
  • Loading branch information
jameskimmel authored Dec 13, 2023
1 parent a0cc15d commit b33bdf8
Showing 1 changed file with 4 additions and 2 deletions.
6 changes: 4 additions & 2 deletions docs/Basic Concepts/RAIDZ.rst
Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ we will allocate on disk:

- one 4K block of data

- one 4K padding block
- one 4K parity block

and usable space ratio will be 50%, same as with double mirror.

Expand All @@ -62,7 +62,9 @@ Another example for ``ashift=12`` and ``recordsize=128K`` for raidz1 of 3 disks:

- one stripe can have up to 2 data parts of 4K size because of 1 parity blocks

- we will have 128K/2 = 64 stripes with 8K of data and 4K of parity each
- we will have 128K/8k = 16 stripes with 8K of data and 4K of parity each

- 16 stripes each with 12k, means we write 192k to store 128k

so usable space ratio in this case will be 66%.

Expand Down

0 comments on commit b33bdf8

Please sign in to comment.