Date: Wed, 2 Jun 2004 13:09:52 -0500 From: Vulpes Velox <kitbsdlist2@HotPOP.com> To: Bruce Evans <bde@zeta.org.au> Cc: freebsd-fs@FreeBSD.org Subject: Re: file space question Message-ID: <20040602130952.49fb2561@vixen42.24-119-122-191.cpe.cableone.net> In-Reply-To: <20040601160031.T18025@gamplex.bde.org> References: <20040531213127.1eb7224c@vixen42.24-119-122-191.cpe.cableone.net> <20040601160031.T18025@gamplex.bde.org>
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On Tue, 1 Jun 2004 16:23:20 +1000 (EST) Bruce Evans <bde@zeta.org.au> wrote: > On Mon, 31 May 2004, Vulpes Velox wrote: > > > Does ufs have the same problem like FAT32, in that if a file > > exists, it will all ways take up atleast 4KB or so, no matter how > > little data it contains? > > Not exactly. ufs has fragments, which normally have size 1/8 of > the block size, so a 1 byte file normally only takes 1/8 of the > block size. However, the default block size is 16K, so fragments > usually take up at least 2K. If nonstandard block and fragment > sizes are used, then the minimum is the same for ufs and msdosfs: > > ufs: block size 4096, frag size 512 > msdosfs: block size 512 > > With FAT32, 512-byte blocks can cover fairly large disks. IIRC, > there can be 2^28 clusters for FAT32, so the maximum is 2^28*512 = > 128GB. The default block size for msdosfs originally grew large (up > to 32K or 64K) back when there was only FAT16 and the limit was 2^16 > or 2^15 clusters. 2*16*32K is just 2GB, so even with the too-large > block size of 32K wasn't large enough for new disks about 10 years > ago. Since then, 4K has become the default for most cases since it > is a good i/o size(still a little too small, but OK with some > buffering), and because using a reasonably large block size helps > stops the FAT size from beoming preposterously large (2^28 clusters > takes 1GB for the FAT). > > Also, msdosfs has much smaller metadata overheads than ufs, so it > can hold a lot of small files in the space that ufs would use for > metadata. The wastage is very noticable on small file systems like > ones that fit on floppy disks. So storing bookmarks and the like each in their own file, on UFS is a bad idea then? Or given modern disk sizes probally can easily be ignored?
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