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From: Ivan Voras <ivoras@freebsd.org>
Date: Mon, 31 Aug 2009 13:18:02 +0200
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Subject: UFS block writing
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Does UFS do full-block writes? Always or only in specific circumstances?

For example, if a UFS file system is created with the 16/2 
block/fragment size, and a small random write (e.g. 512 bytes) comes in 
the middle of a larger file, will UFS read in the whole 16k block, 
modify it and write it out? What about fragments?