[Resending my earlier reply to Eric to the list, since Thunderbird managed to break "reply all" functionality.]
On 02/09/17 09:59, Eric Brown wrote: > I am working with some OpenBSD vmd disk images. They are allocated at > 1T, though they have only a base OS install weighing in at about 6G of > data. > > I am running tarsnap on this sucker, but it never seems to finish. I am > wondering if there is something going on here, such as tarsnap unfurling > the 1T file (but perhaps compresses it supremely well) or if maybe I > just need to be more patient. Sending a SIGINFO should confirm this, but I suspect tarsnap is spending all of its time reading and deduplicating zeroes from the sparse file. It's just possible that the libarchive code is doing something smarter than I remember, but I don't think so. The best workaround I can suggest for this is to find a tool which can archive sparse files -- I think GNU tar has support for this? -- and use that to turn your 1T sparse file into a ~6G non-sparse file. It's not ideal, but sparse files are rare enough that in ten years of tarsnap you're the first person I remember who needed to handle large sparse files... -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
