>we'd know how to get the best performance when writing >absolutely synchronously ie. the data had to actually >end up on a disk platter and not just get parked in >some cache, like in the buffer cache or in the drive >controller's cache.
I should have mentioned why we instrumented rewrite versus append performance, since it's apropos the current metadata overhead discussion. When an existing file (particularly a large file) is rewritten the filesystem code has the opportunity (though not the obligation) to reuse the existing block allocations; this is almost always a win as it requires far less manipulation of the metadata to write the same amount of "real" data. If you instead first delete and then recreate the file from nothing, you typically have to fondle the metadata a whole lot more, which takes time. _______________________________________________ gnhlug-discuss mailing list [EMAIL PROTECTED] http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
