Messages in this thread |  | | | Date | Tue, 01 Aug 2006 10:24:49 +0300 | | From | Avi Kivity <> | | Subject | Re: 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/
|  |