lkml.org 
[lkml]   [2006]   [Aug]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Solaris ZFS on Linux [Was: Re: the " 'official' point of view"expressed by kernelnewbies.org regarding reiser4 inclusion]
Theodore Tso wrote:
>
> Ah, but as soon as the repacker thread runs continuously, then you
> lose all or most of the claimed advantage of "wandering logs".
> Specifically, the claim of the "wandering log" is that you don't have
> to write your data twice --- once to the log, and once to the final
> location on disk (whereas with ext3 you end up having to do double
> writes). But if the repacker is running continuously, you end up
> doing double writes anyway, as the repacker moves things from a
> location that is convenient for the log, to a location which is
> efficient for reading. Worse yet, if the repacker is moving disk
> blocks or objects which are no longer in cache, it may end up having
> to read objects in before writing them to a final location on disk.
> So instead of a write-write overhead, you end up with a
> write-read-write overhead.
>

There's no reason to repack *all* of the data. Many workloads write and
delete whole files, so file data should be contiguous. The repacker
would only need to move metadata and small files.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-08-01 09:27    [from the cache]
©2003-2011 Jasper Spaans