Date: Mon, 6 Mar 95 11:02:20 MST From: terry@cs.weber.edu (Terry Lambert) To: jkh@FreeBSD.org (Jordan K. Hubbard) Cc: current@freefall.cdrom.com Subject: Re: "Sparse" files? Message-ID: <9503061802.AA18642@cs.weber.edu> In-Reply-To: <199503060557.VAA00476@time.cdrom.com> from "Jordan K. Hubbard" at Mar 5, 95 09:57:18 pm
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> Do we have any support for the likes of Linux's sparse files? Patrick > here says it saves around 25% for executables alone when run-length > compression is done for zero'd blocks. This almost requires dual-staging in the FS, such that a block read off of disk can become more than one block in core. This is effectively what you'd want to do blobk-based deterministic compression, for instance adding doublespace support to the DOSFS. I suspect a lot of the speed pickup is that this would effectively cause a read-ahead of however many blocks a single block decompresses to minus one (which is what make this not act as a performance loss in practice). Effective read-ahead for binaries would probably unmask this as a false win. You'd be left with some space savings at a rather steep access penalty. Terry Lambert terry@cs.weber.edu --- Any opinions in this posting are my own and not those of my present or previous employers.
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