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On 27 Jun 2010, at 08:52, Shaochun Wang wrote: |
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> ... "Reserving some number of filesystem blocks for use by |
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> privileged processes is done to avoid filesystem |
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> fragmentation" |
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> |
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> It means that filesystem defragmentation need such reserved blocks to |
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> work properly, am I right? If so, can I make the reserved blocks a |
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> little because the default 5% is too much. My NAS filesystem is about |
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> 7x1.5T, then 5% means a lot of space. |
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|
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I'm pretty sure that just means that Linux will try to put files in |
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contiguous sectors, so they're not fragmented, and that as you run out |
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of space it's generally harder to do that. |
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|
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But I would imagine this is particularly the case with the occasional |
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large file on a typical filesystem cluttered with small files - if you |
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have a 1TB drive and save 9 100GB movie files on it, the remaining |
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free space is going to be contiguous, anyway. |
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|
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Whilst it would be interesting to do some real world testing on big |
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hard drives fulla porn, you can safely set the reserved space to 0% |
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and forget about it. That message has been there since ext2 and if you |
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streaming suddenly starts to stutter when your filesystem is 99% full, |
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well, you were going to add another drive to the array, anyway, |
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weren't you? Add it in and expand the filesystem and see if that makes |
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any difference. |
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Interestingly, I've just done an fsck on my ext4 media array and it |
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shows as 83.8% non-contiguous. It is 1.4TB with 272G or 19% free. I |
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can only assume this is because I also use it for backups, and have a |
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couple of directories on there of many much smaller files. |
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|
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Stroller. |