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XFS: the filesystem of the future?

XFS: the filesystem of the future?

Posted Jan 28, 2012 3:36 UTC (Sat) by sbergman27 (guest, #10767)
In reply to: XFS: the filesystem of the future? by sandeen
Parent article: XFS: the filesystem of the future?

"#1, if your application follows proper data integrity practices (fsync et al)"

And if it doesn't happen to? How many filesystem users do code audits of all the programs their organizations runs, specifically looking for good practice regarding fsync? It's much better to just use a reliable filesystem.

"and your storage is properly configured, you will not lose data on a crash on xfs."

That's reasuring. I note that your recommended finger-pointing re: data loss, is now distributed between user and vendor. But it's definitely not XFS's fault!

"Losing buffered data on a crash is expected with any filesystem,"

No. Losing data on a crash is not "expected with any filesystem". (I've never had a customer quiz me as to whether lost data was "buffered" or not.) EXT3 was rock solid before they ruined it around 2.6.31 or so in the name of performance. A manual adjustment to data=journal should still restore it to its former glory. Though I fear that this new "performance over reliability" mindset in the Linux FS world might be eroding it in other ways, too.

"Ext3 tended to push data out more regularly"

EXT3 tended to keep your data rock solid safe.

"which had its pros and cons"

If I sent out a survey to my customers asking their opinion on reliability vs performance on filesystems, I already know what they would say. Reliability over performance: 100%. Performance over reliability: 0%.

It seems to me that, these days, Linux FS devs either live in ivory towers of performance benchmarks, or in California prisons. But none seem to live anywhere near me. We need more Stephen Tweedies.

-Steve Bergman


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XFS: the filesystem of the future?

Posted Jan 28, 2012 5:53 UTC (Sat) by dlang (subscriber, #313) [Link]

ext3 has always had the possibility of loosing data in a unclean shutdown if you didn't do the fsync dance.

the window of loss was smaller, and most people don't actually have unclean shutdowns that frequently, so I believe you when you say you never experienced it.

but that doesn't mean that ext3 was 'rock solid' in the face of poorly written applications. There are plenty of people who lost data on ext3.

XFS: the filesystem of the future?

Posted Jan 28, 2012 16:37 UTC (Sat) by sbergman27 (guest, #10767) [Link]

The window was *far* smaller. However, the question is not did anyone ever suffer any data loss. It's how many people and how much data in comparison to other filesystems. I know of no other filesystem as resilient at its default settings as was the pre2.6.31 (or so) ext3. I also never noticed any performance problems. Certainly nothing that my customers cared about.

And of course, we can still mount ext3 explicitly data=ordered.

Oh for the days when Linux filesystem devs cared more about reliability than benchmarks... no matter whose fault the data loss might be. Things have changed since the Tweedie days.

Today, I use ext4 with nodelalloc. I tried ext4 at its defaults. But the first time power was lost (and the UPS failed) we had to rebuild a bunch of C/ISAM files. Never in our long history with ext3 did we *ever* have anything like that happen. (And my customers are bad about letting their UPS's go.) Personally, I think nodelalloc should be default, with delalloc available as a mount option.

Current Linux filesystem devs just seem reckless to me.

XFS: the filesystem of the future?

Posted Jan 29, 2012 0:53 UTC (Sun) by dlang (subscriber, #313) [Link]

the current filesystem devs are the same people as they were in the 'good old days'

go talk to a good database admin (or especially a database developer), they will tell you that all filesystems have always had these problems, and they can probably tell you horror stories about ext3 and it's "worst in the industry" fsync performance (it's been documented for a fsync to take 10s of seconds on ext3 vs ms for other filesystems under the same workload)

you can disable all caching by mounting a filesystem with the sync option, but the performance is going to be _so_ horrible (unless you have drives that lie about when the data is safe) that you will end up changing back.

XFS: the filesystem of the future?

Posted Jan 29, 2012 3:09 UTC (Sun) by sbergman27 (guest, #10767) [Link]

"the current filesystem devs are the same people as they were in the 'good old days'"

No. In the Ext world, I hardly ever hear the name "Stephen Tweedie" anymore. And he's the main developer I trusted. A very careful, conservative, and patient devloper. Took forever to get Ext3 out, Which annoyed me at the time. But I've learned to appreciate his "good things come to those who wait" philosophy. Today, it's Ted T'so at the forefront of Ext. A *very* different person.

"go talk to a good database admin (or especially a database developer), they will tell you that all filesystems have always had these problems"

And there you go again. Casting it as "black and white". If Ext3 ever lost a byte of data on someone's machine in Kenya, then by the gods, it's just as bad as the current crop of linux data sieve filesystems.

Hey, if you can keep doing the black and white thing, I can compensate by adjusting the contrast knob a bit. ;-) Current linux filesystems may not be, exactly, data sieves. But they are a far cry from the halcyon days of Ext3 pre 2.6.31.

XFS: the filesystem of the future?

Posted Jan 29, 2012 6:45 UTC (Sun) by raven667 (subscriber, #5198) [Link]

If I sent out a survey to my customers asking their opinion on reliability vs performance on filesystems, I already know what they would say. Reliability over performance: 100%. Performance over reliability: 0%.

I don't believe that is true. If you ask them then sure, they will pick reliability but in actual operations they will performance first most of the time. Witness the popularity of MySQL/myisam which makes that exact trade off, if reliability was the most important thing everyone would use PostgreSQL and no one would have even heard of MySQL. What people actually do and what they say are often diametrically opposed.

XFS: the filesystem of the future?

Posted Jan 29, 2012 20:51 UTC (Sun) by sbergman27 (guest, #10767) [Link]

"I don't believe that is true. If you ask them then sure, they will pick reliability but in actual operations they will performance first most of the time."

No, they would not. None have any complaints about our filesystem performance, either on my CentOS 4 machines using Ext3 mounted data=ordered, or on my later servers with Ext4 mounted nodelalloc. Benchmarking of Ext4 with and without nodelalloc always come out pretty much a wash. I've never understood what the fuss was about. Delayed allocation just doesn't improve performance noticeably. Nor did Ext3 with data=ordered in any of the server scenarios I have been involved with. And I see no appreciable difference regarding fragmentation rates, either.

If you've done your own benchmarks with your own server workloads which disagree with mine, I would be interested in hearing about them.

But regarding delayed allocation in ext4 and xfs, and the "wonders" of making data=writeback the default for ext3, I must observe that the Emperor has no clothes.


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