Date: Tue, 26 Feb 2008 19:45:03 +0100 From: "Martin Laabs" <martin.laabs@mailbox.tu-dresden.de> To: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: emulate an end-of-media Message-ID: <op.t65addgm724k7f@martin> In-Reply-To: <20080226075102.GE83599@server.vk2pj.dyndns.org> References: <op.t63j2veq724k7f@martin> <20080225154455.4822e72a@bhuda.mired.org> <20080226075102.GE83599@server.vk2pj.dyndns.org>
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Hi, > I'm not sure wheher Martin is trying to create a dump that is a single > logical volume split over multiple physical volumes or a multi-volume > dump. I want to make a real multi-volume dump over multiple media. Because if I had only one big volume I'd - in the worst case - have to insert all media also if i want to recover only one file. And worser: I'd had to read and decompress all media up to the end. I could of cause use another backup backend but I think dump is one of the best and reliablest backup mechanism. (Because it works on inode-basis and not the user file-system level.) > I suspect Martin is trying for the latter case - which has a number of > advantages (like partial restores are much faster and a failed write > can be retried on new media). But it also has some gotchas. The > biggest one is that dump needs to be able to write past EOM (so it can > record an end-of-volume block). Oh - that are bad news. Do you know how many blocks/bytes dump needs afterwards? > [...] But it does mean that > your magic device needs to be able to return EOM to dump early enough > that dump can record end-of-volume and the compressor can dump that > block and any trailing state before it runs out of media. And it makes the idea to convert a sigpipe to an EOM useless. I've to think about that. (I thought I could just change dump in that way that it handle a sigpipe like an EOM which would be very easy.) Maybe I now have to implement the output byte counting of the script or pipe specified by -P when -B was given. Thak you, Martin L.
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