Date: 30 Apr 1999 00:01:11 +0200 From: naddy@mips.rhein-neckar.de (Christian Weisgerber) To: freebsd-stable@freebsd.org Subject: Re: Does tar do sparse files these days Message-ID: <7gakr7$ep0$1@mips.rhein-neckar.de> References: <7g7vdc$3e6$1@mips.rhein-neckar.de> <199904291758.NAA25146@po1.bbn.com>
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Dennis Rockwell <dennis@bbn.com> wrote: > You would have to do run-length encoding of all strings of > nulls above some small threshhold, regardless of their > alignment, then always seek over these strings when > retrieving. Right. > Since, as you say, the API doesn't reflect these holes, manufacturing > new holes isn't a problem, and even saves some disk space. I'm under the impression that holes are a bad idea in a swap file. But since you need to apply the above heuristic only if stat.st_blocks suggests holes in the first place, this is likely not a problem. Beware of making holes unconditionally, though. > I don't know if the file format would support this, and I > wouldn't expect something this CPU-expensive to be the > default behavior. As I mentioned previously, you can enable this with "-S" for GNU tar. The POSIX ustar format doesn't support it, so all tar's that offer such an option implement it by way of some format extension. -- Christian "naddy" Weisgerber naddy@mips.rhein-neckar.de 100+ SF Book Reviews: <URL:http://home.pages.de/~naddy/reviews/> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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