Date: Sun, 08 Aug 2010 13:13:46 -0400 From: Bill Moran <wmoran@potentialtech.com> To: Kiswono Prayogo <kiswono@gmail.com> Cc: freebsd-questions@FreeBSD.org Subject: Re: File System Performance on FreeBSD Message-ID: <4C5EE5CA.2090706@potentialtech.com> In-Reply-To: <4C5EB94F.509@gmail.com> References: <4C5EB94F.509@gmail.com>
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On 8/8/10 10:03:59 AM, Kiswono Prayogo wrote: > Is there any justification for this benchmark? > > http://www.phoronix.com/scan.php?page=article&item=zfs_ext4_btrfs&num=2 > <http://www.phoronix.com/scan.php?page=article&item=zfs_ext4_btrfs&num=2>; Kind of hard to do much with that "benchmark" First off: * Does the author even know what he's doing? All that article does is display the charts, then tell you what the chart says. The author shows no understanding of what's going on. * He's running the tests on a laptop. * He had a single disk/partition, which was the same disk/partition that he was running the OS off. The difference in speed might have been the result of different software being installed on the different OS that was competing for disk usage. * All of his tests involve tiny amounts of data and/or extremely quick run times (less than 30s). On a system with 4G of ram, the different caching policies on the different FS can have a huge difference on the results. While it's interesting to study those caching differences, it's not anywhere indicative of overall FS performance. Let him run one of those tests for 5 mins and see if the results are still the same. But, most importantly, his benchmarks are useless for any productive use. He doesn't describe the tests he's doing with enough detail for anyone else to attempt to reproduce them and attempt to address the problem. What does he mean by "gzip test"? Can I see the command line parameters involved? How many runs of each test did he do? What other programs were accessing the disk at the time? What other programs were _running_? There's nothing wrong with PC-BSD, but it installs a lot of stuff at install time -- there may be programs running that are hurting the results that aren't running on Ubuntu. Since that was a laptop, what is the powersave policy for the disks in each case? Did he do a single run of each test? That produces the most unreliable results ever. Overall, it's just sloppy reporting if you ask me. For all I know, he actually did a really good job of making sure that everything was set up to be fair, but the article doesn't say that. It's pretty typical of most reporting, not enough depth or care to be useful. I'm sure there are Linux people who will be shouting about this all over the place. But to the casual observer, all this tells you is that Linux's filesystems _may_ be faster for short, bursty work. To someone technical who might be looking to investigate the results with an eye toward fixing them, it's useless. -- Bill Moran
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