Date: Tue, 16 Nov 1999 12:46:54 -0800 (PST) From: Alfred Perlstein <bright@wintelcom.net> To: Zhihui Zhang <zzhang@cs.binghamton.edu> Cc: freebsd-fs@FreeBSD.ORG Subject: Re: On-the-fly defragmentation of FFS Message-ID: <Pine.BSF.4.05.9911161245250.12797-100000@fw.wintelcom.net> In-Reply-To: <Pine.GSO.3.96.991116111847.9599A-100000@sol.cs.binghamton.edu>
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On Tue, 16 Nov 1999, Zhihui Zhang wrote: > > After studying the code of ffs_reallocblks() for a while, it occurs to me > that the on-the-fly defragmentation of a FFS file (It does this on a per > file basis) only takes place at the end of a file and only when the > previous logical blocks have all been laid out contiguously on the disk > (see also cluster_write()). This seems to me a lot of limitations to the > FFS defragger. I wonder if the file was not allocated contiguously > when it was first created, how can it find contiguous space later unless > we delete a lot of files in between? > > I hope someone can confirm or correct my understanding. It would be even > better if someone can suggest a way to improve defragmentation if the FFS > defragger is not very efficient. > > BTW, if I copy all files from a filesystem to a new filesystem, will the > files be stored more contiguously? Why? > > Any help or suggestion is appreciated. I think you're missing an obvious point, as the file is written out the only place where it is likely to be fragmented is the end, hence the reason for only defragging the end of the file. :) -Alfred To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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