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Benchmarking Linux Filesystems Part II
Anonymous Coward writes "Linux Gazette has a new filesystem benchmarking article, this time using the 2.6 kernel and showing ReiserFS v4. The second round of benchmarks include both the metrics from the first filesystem benchmark and the second in two matrices." From the article: "Instead of a Western Digital 250GB and Promise ATA/100 controller, I am now using a Seagate 400GB and Maxtor ATA/133 Promise controller. The physical machine remains the same, there is an additional 664MB of swap and I am now running Debian Etch. In the previous article, I was running Slackware 9.1 with custom compiled filesystem utilities. I've added a small section in the beginning that shows the filesystem creation and mount time, I've also added a graph showing these new benchmarks." We reported on the original benchmarks in the first half of last year.
An interesting analysis in every aspect, and it's fine and dandy for the person who uses 400 GB drives and a ATA controller on a 500MHz computer but I'd like to see how the filesystems compare on a bigass RAID system run by a Power5 server, or a few Itaniums that usually have with a few hundred connected users. Something a bit more "entreprise" - where the choice of a filesystem is a bit more critical than a small server or a home PC.
One thing this does show is that you need to be very careful to match the filesystem type to the main tasks the PC is going to be used for. Personally, there's no real clear winner as all have major gains or deficiencies in some areas. One very interesting point was the vast difference in the amount of available space after a partition and format between the different filesystems.
Conor "You're not married,you haven't got a girlfriend and you've never seen Star Trek? Good Lord!" - Patrick Stewart
It is widely known that Reiser filesystems are heavy on CPU usage 4 more than 3. These benchmarks seem to show a CPU bound IO situation as opposed to an IO bound IO situation. As an earlier comment pointed out, the hardware used in this test was a 500mhz CPU. My slowest computer is a 1000mhz system, which is usually IO limited, not CPU limited. I'd be interested to see these same benchmarks run on real hardware, or some more complex benchmarks (random RW, DB load, etc.). The hardware used for this test would be suitable for a fileserver, but not much else. In that situation, E2, E3 or XFS are probably the right choices as it points out. What about desktop loads, enterprise loads, or something more interesting?
--Brandon
Here's what's missing. They forgot to tell you how well the drive performed after being used for 1 year, and having constantly moved data from one place to another, and constantly deleting and creating new data. It would have been a better test if the drive was about 75% full, with data from 2 years of use, and then the same tests were performed.
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I love the CPU utilization graph for "touch 10,000 files".
A quick glance shows ReiserV4 as much more CPU intensive, you have to look at the scale to realize it only used 0.3% more CPU.
His benchmark data is ruined by using a gross unrealtistic piece of hardware - modern fast hard disks coupled with a cpu which is absurdly slower than anything you can buy.
There were some current (recent 2.6 kernel with XFS, JFS, possibly Reiser4, etc) benchmarks done on highend servers (or at least something with drives a few steps up from the CompUSA weekly special), especially if anyone wants to see Linux succeed in the enterprise.
Based on the geometric mean of all the benchmark times for each filesystem, which effectively weights all benchmarks equally:
JFS won
EXT2 and EXT3 took 17% longer than JFS
XFS took 29% longer than JFS
Reiser3 took 38% longer than JFS
Reiser4 took 52% longer than JFS
Now, 1.52 seconds is not a whole lot longer to wait than 1 second. With any luck we'll see a post from Hans explaining why Reiser4 took longer, or what sacrifices were made to make the others faster, if there are any.
I'm no expert by any means, but I think the idea behind the ReiserFS is breaking down the FS paradigm from the file level to the line level.
There is the classic example from the Reiser website. If your password file gets hacked, you have to ditch the whole file if you're using traditional file systems. You only know whether or not the file's been changed. However, with the Reiser system, it can tell you *what line*, and thus which user/password, was changed.
That's just a taste of where you can go with the ReiserFS. There are other things coming down the pipe; check out the reiser website for a better idea of the new features that ReiserFS promises.
Computers are useless. They can only give you answers.
-- Pablo Picasso
Reiser is not designed for slow CPUs. AFAIK, a key part of the design was the Hans Reiser realised that CPUs were vastly underused. IO resources were maxed out and CPUs were sitting idle. So he found ways to use the CPU to make more efficient use of the IO resources. So this benchmark on a 500Mhz machine will of course show Reiser in a bad light, and moving lower down to a 266Mhz will make it even worse.
For a decent benchmark of how filesystems work on modern hardware: use modern hardware.
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It would be interesting to see the results of the same tests running against a SCSI drive system where there is less IO overhead to see if the results differ.
There are other considerations here as well. What about the I/O elevator's tuning options.
Yes, I'd much rather see this test occur against a SCSI drive or better yet against a RAM drive for pure software performance.
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-Joe Baker
Huh? Sorry, did you read the same graphs or are you just trolling?
This article shows that ext2 and ext3 are close to the top performer in most tests and do not have many "worst-case scenarios" (unlike, e.g. Reiser3 and Reiser4).
If there is anything that you can conclude after reading this study, it is that ext3 is a reasonably good default choice for a filesystem.
Anyway, how is the average user supposed to be concerned by these results?
In my daily work I manage hundreds of GB's of data and have hardly seen a significative difference between XFS, JFS and ReiserFS v.3 on relatively modern hardware (Tyan S2882 Pro motherboard, two Opteron 244 processors, 4 GB RAM and two 250-GB SATA HD's) running OpenSuSE 10. I put the most important data on a XFS partition but also have a small ReiserFS partition which can be read from Windows.
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What am I saying? I want to know how efficent these filesystems are in packing the data on the HD.
I'm glad that you get more data out of Reiser v4, JFS, and XFS at formatting time, but my feeling is that Reiser v4 (once profiled, tweaked and refined for speed and space) will pack data tighter than anyone else. Meanwhile, I'm looking for something like ext3 that packs better.
--
# Canmephians for a better Linux Kernel
$Stalag99{"URL"}="http://stalag99.net";
XFS does things that ext? and Reiser can't do. Reiser does things other FSes don't do as well. It's a true 64-bit filesystem and it supports insanely large filesystems, up to 9 million terabytes in 64 bit mode (with a 64 bit kernel.) It even provides realtime support, although I guess that's still beta in linux? It can be defragged and even dumped while live. It has insanely quick crash recovery. And of course, it does other stuff too; check the project page. XFS may not be the fastest filesystem - it may even be the slowest - but it's got features no other filesystem has. If you need them, XFS is the winner. Hell, if you just trust XFS more than you trust other filesystems, it's the winner. (Sorry, but I wasn't sleeping when reiser was eating everyone's data, and ext3 handles corruption much more poorly than any of the other Journaled options.)
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
I'm *sick* of reading filesystem benchmarks of people who doesn't even care about even reading the documentation of the filesystems they compare
OK, so ext3 is not the fastest filesystem on earth. But it has some default options which makes it suck even more than it usually do, and those options are *documented* in Documentation/filesystem/ext3.txt
* Ext3 does a sync() every 5 seconds. This is because ext3 developers are paranoid about your data and prefers to care about your data than win on benchmarks. Syncing every 5 seconds ensures you don't lose more than 5 seconds of work but it hurts on benchmarks. Other filesystems don't do it, if you are doing a FAIR comparison override the default with the "commit" mount option
* ext3's default journaling mode is slower than those from XFS, JFS or reiserfs, because it's safer. When ext3 is going to write some metadata to the journal, it takes care of writting to the disk the data associated to that metadata. XFS and JFS journaling modes do *not* care about this, neither they should, journaling was designed to keep filesystem integrity intact, not data, ext3 does it as an "extra", and it's slower because of that. But if you want to do a fair comparison, you should use the "data=writeback" mount option, which makes ext3 behave like xfs and jfs WRT to journaling. Reiserfs default journaling mode is like XFS/JFS, but you can make it behave like the ext3 default option with "data=ordered"
ext3 is not going to beat the other by using those mount options, but it won't suck so much, and the comparison will be more fair. And remember: ext3 tradeoffs data integrity for speed. There's nothing wrong with XFS and JFS, but _I_ use ext3.
If someone does not know that filesystem benchmarks that take less than a tenth of a second are meaningless, it makes you wonder if they made errors in other aspects as well. These results are not consistent with the results that we have had. I bet he did not make an effort to ensure that you had to read the disk for these benchmarks, that he did not copy his file set from the same fs as he was measuring (makes a HUGE difference to performance and it is the mistake every beginner makes), etc. You'll note that the way he makes his graphs makes 1% differences look huge, etc.
I would rather see these benchmarks on a computer less than 5 years old. I would also appreciate an open source version of the tests so they could be reproduced. For ease of reading, I think the article should be on a separate page on the site as well.
/usr/bin/touch
/dev/zero stuff is completely bogus. No indication of the blocksize that was used.
I've got a screaming Dell 1.6 GHz P4 to test with and here are my results for a couple of tests it only has ext3 and a whatever cheap harddrive came with the box. I'm not sure if dma is enabled or if I've done any hdparam tunings, but I'm not sure of their test system either:
my touch 10,000 files: 24.314 seconds theirs 48.25
I used a shell script that called
Now if I use a Perl open() call, I get 8.887 seconds
Now with a cheesy C that uses fopen() and fclose() I get 4.639 seconds
my make 10,000 directories: 56.832 seconds theirs 49.87
that is a shell script
If I user perl, I get 35.171 seconds
The
The copy kernel stuff to and from a different slower disk with an unknown filesystem on it is useless.
The split tests are not indicative of anything in real life, and they took on order of between 60 seconds and 130 seconds to perform on their 500MHz system with most being in the 130 second range. I got 16.547 seconds.
I do not see how any relevant information can be obtained from this article. I'm disappointed in the Linux Gazette and Slashdot for printing this information.