Date: Tue, 17 May 2005 07:44:40 -0500 (CDT) From: "Viren Patel" <virenp@mail.utexas.edu> To: "Jerry McAllister" <jerrymc@clunix.cl.msu.edu> Cc: Kris Kennaway <kris@obsecurity.org> Subject: Re: Transferring dump file to tape? Message-ID: <1220.66.25.129.27.1116333880.squirrel@mail.cm.utexas.edu> In-Reply-To: <200505161952.j4GJqXjB027333@clunix.cl.msu.edu> References: <36710.146.6.178.5.1116269538.squirrel@mail.cm.utexas.edu> <200505161952.j4GJqXjB027333@clunix.cl.msu.edu>
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>> >> > On Mon, May 16, 2005 at 11:36:18AM -0500, Viren Patel >> > wrote: >> >> Hello. I am using 'dump' to backup client filesystems >> to >> >> a >> >> disk file on an NFS mounted partition, e.g. >> >> >> >> dump -0aLu -f /bk/var-20050516 /var >> >> >> >> Now I'd like to take the backup file (var-200500516) >> and >> >> move it to tape (on the NFS server). However I'd like >> >> the >> >> tape to have the data just as if it had been created >> >> directly by 'dump', e.g. >> >> >> >> dump -0aLu -f /dev/nsa0 /var >> >> >> >> Any way to do this? >> > >> > You can use dd to write a file to a device (e.g. >> tape). >> > >> > Kris >> > >> >> I thought so too, but it doesn't work. When I issue >> >> dd if=var-20050516 of=/dev/nsa0 >> >> I get the following error: >> >> dd: /dev/nsa0: Invalid argument >> 1+0 records in >> 0+0 records out >> 0 bytes transferred in 0.000786 secs (0 bytes/sec) >> >> Since 'dump' works with /dev/nsa0 I am not sure what the >> problem is. > > I would expect the dd to work also. You may need to do > something > with blocksize. > > But, we see that error a lot on different machines while > attempting > to write a file to a tape. We have code that opens the > drive and > writes directly to it, other places that attempt to use dd > and also > some places that try to cat to the drive. All of them > work most of > the time, but fail consistently on some machines that > appear to be > otherwise identical. We have resorted to numerous tricks > to write > to a tape on a system that is failing, usually to no > avail. The error > you report is the one we see with dd. I generally don't > see any > other console message or anything that shows in a dmesg. > > I would very much like to see someone who really knows > about writing > tapes respond to this. I have begun to be suspicious > that there is > something weird about the the sa driver or something along > the line, > but don't know enough to really dig it out. I posted > some questions > around 3 years ago, but got no response. > > By the way, this has occurred in various versions of > FreeBSD from > around 3.2 through 4.9. I haven't experimented with it > on 5.xx yet. > > ////jerry > >> >> Viren > Thanks for your input. As per Kris' suggestion adding the blocksize worked for me. 'mt' reports my tapedrive having a blocksize of 1024 bytes (1k), so my command was dd if=var-200501516 of=/dev/nsa0 bs=1k I transfered the dump file to tape and then was able to restore directly from tape. My test dump file was small (140K) but today I plan to test with a full-size multi-gigabyte dump file. I haven't played long with dd to judge its reliability. While I was looking around, I also came across sdd (/usr/ports/sysutils/sdd), which claims to be a better dd replacement. Viren
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