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Am 27.06.2010 09:52, schrieb Shaochun Wang: |
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> Hi: |
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> |
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> I want to tune my ext4 filesystem of NAS data partition to free its |
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> reserved space by using "tune2fs -m0 <partition>". By reading the |
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> manual of tune2fs, I observed the following words: |
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> |
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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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|
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It's not meant for defragmentation but to avoid fragmentation in the |
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first place. Simply speaking, as long as there is enough free space on |
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the disk, even if it is not accessible by an ordinary user, the system |
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can put new data in any place it seems fit. |
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|
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If the disk is really near 100% full, the system has to squeeze new data |
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in every small hole somewhere on the disk. If this is done over a longer |
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time, maybe by deleting files and creating new ones, it massively |
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increases fragmentation. |
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|
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Besides, reserving some space for root can save your rear-end in case |
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some user fills up your root partition. As long as root's processes |
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still have a bit of disk space available, he can still log in and clean |
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up the mess. |
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|
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I agree with you that reserving 5% of several TB is too much for these |
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purposes. I think reducing it to a few 100MB is sufficient. |
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|
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Hope this helps, |
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Florian Philipp |