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Date: Fri, 24 Sep 2010 17:05:42 -0700 From: Taras Glek <tglek@...illa.com> To: linux-ext4@...r.kernel.org Subject: Minimizing fragmentation in ext4, fallocate not enough? Hi, I noticed that several random IO-heavy Firefox files got fragmented easily. Our cache suffers most. The cache works by creating a flat file and storing fixed-size entries in it. I though if I fallocate() the file first, then all of the writes within the allocated area would not cause additional fragmentation. This doesn't seem to completely cure fragmentation with ext4 in 2.6.33. If I allocate a 4mb file, it gets more and more fragmented over time. fallocate() does reduce fragmentation, but not as much as I expected. I assumed that writing to an fallocate()ed area will not cause additional fragmentation. Is my assumption incorrect? Thanks, Taras ps. I'm using filefrag for measuring fragmentation. ps2. Does running filefrag on a directory mean anything in ext4? -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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