Date: Mon, 6 Mar 1995 16:41:27 +1000 From: Bruce Evans <bde@zeta.org.au> To: current@freefall.cdrom.com, jkh@FreeBSD.org Subject: Re: "Sparse" files? Message-ID: <199503060641.QAA15475@godzilla.zeta.org.au>
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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. ffs certainly supports holes in regular files. Gnu cp preserves holes in regular files and creates them if possible, at least on POSIX file systems for which stat() returns suitable non-POSIX info (st_blocks and/or st_blksize). Our cp neither creates them nor preserves them. It might be difficult to support them and still use mmap(). The usual ffs block size is 8K, while the usual linux block size is 1K, so the chance of finding a zero block to compress is much lower. Bruce
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