Development update: Journaling

We are forging ahead with development of the next SAM-QFS release. Although, I cannot make any promises about features (This is software development after all), I wanted to provide a peek at some of our feature development. I'll try to provide these updates on a regular basis. I hope you find these useful.


Journaling

One of the features we are working on is journaling. Some of the benefits of jounaling to QFS are reduced need for samfsck and increased metadata performance. While QFS has a consistency model that generally does not require an fsck, except to reclaim lost space and clean up orphan inodes, journaling will reduce the need for this type of clean up after a panic. The bigger benefit to QFS is the increase in metadata performance. Journaling can reduce the frequency of disk accesses required for metadata-intensive applications. This boosts the performance of QFS. In some preliminary tests, we have already seen a significant increase in performance on Shared QFS clients with journaling enabled on the metadata server. I'll try to report some real numbers as development progresses.

'til next time, Ted

Comments:

What I would very much like to see is:
- Support for VTL device
- get ride of diskvols.conf file which is a very thing to keep track of disk volumes. it would be better to handle disk volumes the same way as tape volumes : in a catalog that is not manually editable

Posted by Selim on February 02, 2008 at 01:26 AM CST #

word "bad" was missing in previous comment:

get ride of diskvols.conf file which is a very "bad" thing to keep track of disk volumes.

Posted by Selim on February 02, 2008 at 01:27 AM CST #

I'd be cautious about adding journaling. I have an application that needs to write data to the disk as fast as it can read it off a gigabit line. I'm nervous that journalling would increase the standard deviation of the write speed too much and make it unusable for me. That's been my experience with other journalled file systems (e.g. ext3, ReiserFS).

Posted by E_Jones on February 08, 2008 at 04:52 AM CST #

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Ted Pogue

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