First Journaling FS for Linux

wendyW writes "LinuxPR has the press release from Namesys, announcing the stable release of the journaling version of ReiserFS. According to the press release, journaling wound up making it even faster than it already was. "

Comments

Journaling File System

[keytoe]

This would be a huge boon to those of us trying to truly break free of the commercial unices. I've had to put together quotes for enterprise quality database solutions before and there have always been a couple of hurdles to get past when considering an Intel/linux based system.

PostgreSQL works wonderfully with large data sets, but lacks the ability to do hot restores. I'm eagerly awaiting that one... Now that it does a much better job with concurrant locks, that's my only real hesitation at this point.

SMP has come a long way in a short time with linux, but is still a bit lacking. This makes it difficult to settle on Intel hardware - sometimes, you just need Raw Horsepower. I'd like to get there without having to buckle down and buy a Sun or HP box. I'm not worried about this one - things are coming along quite nicely...

Now, my last concern was journaling filesystems - and it looks like it's coming at long last! I was excited when the initial announcement was made, but now that the code is out (and Alan is even considering merging into the stable branch!), I'm all gushy inside! Let's hear it for our team!

I've watched this whole linux thing start out as a 'hobby OS' and develop through adolescence into what is becoming a damned serious contender with the big boys. Sure, they're baby steps at the moment, but at this pace, they add up right quick. God, I love this industry - never know what's gunna happen next. Who knows - maybe the government will sue Microsoft for anti-trust violations next. Oh... right...

Selling GPL Exceptions

[crow]

This is not the first time software has been released under this model. My understanding is that this is how RT Linux was released.

[The idea of RT Linux is to put a small real time kernel underneath Linux. This kernel handles the real time tasks, and schedules Linux when a real time task doesn't require it. It also provides a communication mechanism between Linux processes and real time tasks.]

So the RT linux kernel could, in theory, be used without Linux (perhaps with another OS instead) to provide real time services. The author has carefully retained the copyright to his code, so he can sell it under a non-GPL license if someone wishes to incorporate it into a commercial project.

I'm not aware of any non-GPL licenses for RT Linux, but the model is there.

The main thing that helps make this model work is that the copyright holder controls the distribution. That means that in order to get your changes into the official releases, you have to resolve any copyright issues. It only breaks down if there is a significant dispute and someone is willing to go to the effort to start a separate distribution. Of course, if they get the file system into the main Linux distribution, that action will trigger a fork in development.

Re:Deletion times

[Jeff Mahoney]

There is a semi recent benchmark vs ext2fs at http://name sys.botik.ru/~yura/benchmarks/journal_227/ext2_vs_ jour9.html

Chris has the office next to mine and has been showing me these benchmarks just about every day - they improve just about every day.

-Jeff

Important, but likely not for DBMSes

[Christopher B. Brown]

I hate to take issue with a well-spoken posting, but journalling is not of primary usefulness for helping support High Availability RDBMS systems.

The main effect of journalling, the thing that is really important about it, is that it guarantees that metadata updates are kept consistent. That is, journalling is primarily supportive of making sure that filenames, directory structures, permissions, and such are kept consistent even when moderately catastrophic things happen.

This is a really good thing when supporting file serving activities, as that indeed tends to involve lots of manipulations of files as users shift them around.

I've been on the ReiserFS mailing list since '97; have been running a personal news spool on a small ReiserFS partition for probably 6 months. I can't tell for sure if the journalling now available is metadata-only, or if it also journals normal data updates. It looks rather more like metadata-only, which is useful for file-server work, but not so much for RDBMSes.

Databases behave in quite different ways from file servers in terms of the way they do file access.

If you look at most RDBMSes, they create a few files, and do lots of manipulations on top of them. Informix SE is a counterexample, basically using Informix C-ISAM underneath, but is unusual in that regard. If you look at the database partitions, you get one of two things:

• Partitions containing a few very large files.

  Note that for these, the metadata is very static which means that journalling of metadata is of relatively little importance.

• Partitions containing no filesystem, but rather raw data being managed by the RDBMS.

  Don't just believe me; I am not the ultimate authority on this. Transaction Processing : Concepts and Techniques is a rather definitive reference; it discusses methods of managing transactions in the context of database management systems, and goes into considerable detail discussing transaction logging, which bears striking (and not merely coincidental) resemblance to journalling.

  The critical point here is that it is the database manager that wants to manage the logging/journalling; Oracle and Sybase and IBM and Informix will be loathe to pass on responsibility for this to Hans Reiser, wonderful guy though he is.

Conclusions

1. Sorry, I have to disagree with you on ReiserFS being of fundamental importance to those doing serious database work.

   What will be of fundamental importance will be when Stephen Tweedy's Raw Device Support gets integrated into the "production" kernels. That is what Oracle is looking for (consider: Oracle has pumped some funds into RHAT, and RHAT is paying Stephen Tweedie... Could there be some connection?)

2. Journalling IS important for sorts of applications that manipulate lots of files, which includes things like dynamic web serving and file serving.

   Even if this isn't such a boon to those doing serious RDBMS work, it can still be a boon to lots of other folks...