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Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration)Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration)Posted Apr 26, 2006 2:49 UTC (Wed) by sbergman27 (subscriber, #10767)In reply to: Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration) by dlang Parent article: Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration)
There is a difference between the benefits "not counting" and the guarantees not being absolute.
But you are correct. Hardware write caching does figure in.
You *can* turn write caching off on most IDE drives but, as you say, there is a considerable performance penalty due to the insane limitation on write request size imposed by the ATA standard. So far as i know, SCSI drives are not so hampered.
P.S. Did I say something about the drive using its platter energy for something?
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Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration) Posted Apr 26, 2006 7:28 UTC (Wed) by dlang (✭ supporter ✭, #313) [Link] no, you didn't say anything aobut platter energy, but it's a common misconception that people have about drives and the cache on them
Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration) Posted Apr 26, 2006 15:14 UTC (Wed) by sbergman27 (subscriber, #10767) [Link] I saw refernces to that misconception twice yesterday. Oddly, the last time I encountered it (that I remember) was in 1979 when my first computer science instructor made reference to the "fact" that the drive did that. I believed it at the time, and then later decided it was urban legend.
I notice in your previous post you indicate that they don't do that "anymore". Did they really used to do that?
Also of note, and sorry, I don't have a ready link, I was once struck by a thread on lkml in which someone was crash testing different filesystems under Linux. He had a filesystem with lots of writes going on and knew what all the md5sums should be or something like that and would then pull the plug at random times and observe what happened. His question to the list was for someone to please point out what he was "doing wrong". You see, all the other filesystems in the test corrupted files with more or less the same frequency. All except for ext3, that is. It seemed never (or very rarely) to ever corrupt files and he felt that there must be a problem with his methodology. It was explained that ext3 defaults to data=ordered mode and that such behavior was really expected.
My summary of the thread is probably not completely accurate because it's been a while since I read it, but I was struck by the fact that someone observed the difference even though they were not expecting it.
If I can dig up a link, I'll post it.
Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration) Posted Apr 26, 2006 16:15 UTC (Wed) by dlang (✭ supporter ✭, #313) [Link] >I notice in your previous post you indicate that they don't do that "anymore". Did they really used to do that?
I don't know for sure, but every urban legend needs to get started somewhere right? :-)
thinking about it from a practical standpoint, at one point drives had very small buffers (ram was too expensive, and too large to put much on a drive) along with a lot of rotating mass, so it would have been possible to flush that buffer immediatly on power-loss (and the tolorances of the data on disk were loose enough to accept the slight distortion that would result).
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