:Hell Low.
:
:I think we should conduct a slight PR move
:and update [1] w.r.t HAMMER.
Well, if someone wants to correct it, sure. I haven't made any
edits to wikipedia in a long time so it generally doesn't let me
edit without creating a hassle.
:What can be said about data layout?
:The table at [1] has following columns:
:? Block suballocation
:? Variable file block size
:? Extents
Each block is indexed via the B-Tree. The block size is variable but
the current implementation limits itself to 16K and 64K block sizes.
Extents are theoretically doable but the current implementation
does not use extents.
:? Allocate-on-flush
Hybrid allocation model. Reserve on write, allocate on flush.
:+ Sparse files
Yes.
:- Transparent compression
:
No.
:What are those limitations for HAMMER?
:? Maximum filename length
255 chars.
:? Allowable characters in directory entries (are there exceptions?)
No limitations except for '/' of course.
:? Maximum pathname length
Limited by the OS (typically 1024).
:? Maximum file size
Approximately 2^63 bytes
:
:Does it support ACLs, Security/MAC labels,
:extended attributes, alternate data streams, forks?
No.
:What can be said about CoW, Block journaling or
:Metadata-only journaling of HAMMER?
:Can something be said w.r.t XIP [2]?
Infinite fine-grained automatic snapshots.
:I guess HAMMER volume still cannot be shrunk,
:nor can it deduplicate.
No, though dedup is easy to do. There were no takers on the dedup
GSOC project though.
-Matt
Matthew Dillon
<dil...@backplane.com>
:[1] http://en.wikipedia.org/wiki/Comparison_of_file_systems
:[2] http://en.wikipedia.org/wiki/Execute_in_place
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