18 messages in org.freebsd.freebsd-fsRe: ZFS and disk usage| From | Sent On | Attachments |
|---|---|---|
| Mark Schouten | Apr 13, 2012 5:20 am | |
| Volodymyr Kostyrko | Apr 13, 2012 6:10 am | |
| Mark Schouten | Apr 13, 2012 6:28 am | |
| Peter Maloney | Apr 13, 2012 6:32 am | |
| Johannes Totz | Apr 13, 2012 8:26 am | |
| Tom Evans | Apr 13, 2012 8:44 am | |
| Freddie Cash | Apr 13, 2012 8:45 am | |
| Freddie Cash | Apr 13, 2012 8:49 am | |
| Volodymyr Kostyrko | Apr 13, 2012 9:32 am | |
| Ronald Klop | Apr 15, 2012 4:14 am | |
| Mark Schouten | Apr 16, 2012 1:35 am | |
| Volodymyr Kostyrko | Apr 16, 2012 11:32 pm | |
| Mark Schouten | Apr 17, 2012 1:37 am | |
| Volodymyr Kostyrko | Apr 17, 2012 2:54 am | |
| Mark Schouten | Apr 17, 2012 3:02 am | |
| Volodymyr Kostyrko | Apr 17, 2012 3:10 am | |
| Mark Schouten | Apr 17, 2012 3:22 am | |
| Mark Schouten | May 3, 2012 2:28 am |
| Subject: | Re: ZFS and disk usage | |
|---|---|---|
| From: | Freddie Cash (fjwc...@gmail.com) | |
| Date: | Apr 13, 2012 8:45:33 am | |
| List: | org.freebsd.freebsd-fs | |
On Fri, Apr 13, 2012 at 8:27 AM, Johannes Totz <joha...@jo-t.de> wrote:
Without checking the numbers myself... Note that zpool and zfs do not agree on (free) space accounting: zpool shows "raw" space, whereas zfs includes metadata overhead for itself.
Small rant: I dont understand why zpool and zfs show different things. If you have an integrated storage stack then why not show consistent numbers? Is there any use for this extra (mis-)information that zpool-vs-zfs provides?
There's a great posting about the differences in the zfs-discuss mailing list archives, although I can't find a reference to it at the moment. Going from memory, the breakdown is something like:
zpool shows "raw storage available to the pool across all vdevs", without counting any redundancy. This should be approx. "size of drives * num of drives".
zfs shows "storage space available for use", after removing all redundancy, extra space for metadata, checksums, etc. This is what's available for programs to use, before compression and dedupe take effect.
df shows "storage space available to userspace programs" after all compressions, dedupe, metadata, checksums, etc have been removed. This is the actual space that users can access.
"ls -l" shows the "size of files" (as in, uncompressed, rehydrated, the size it would be if you copied it to a floppy).
They each work on different layers of the storage stack (DMU, ZPL, userspace, etc). Hence, they show different values. But once you think about what each layer of the stack is doing ... the numbers make perfect sense.
-- Freddie Cash fjwc...@gmail.com
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