Date: Sat, 2 Mar 2002 07:51:27 -0800 From: "Drew Tomlinson" <drew@mykitchentable.net> To: "David Smithson" <david@customfilmeffects.com> Cc: <freebsd-questions@freebsd.org> Subject: Re: defragment UFS Message-ID: <003301c1c202$1d24d200$1e01a8c0@lc.ca.gov> References: <002301c1c1a6$b9e06f70$0801a8c0@ethel> <20020302050142.GB1634@raggedclown.net> <3C807A58.1030209@customfilmeffects.com>
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----- Original Message ----- From: "David Smithson" <david@customfilmeffects.com> Cc: <freebsd-questions@freebsd.org> Sent: Friday, March 01, 2002 11:08 PM Subject: Re: defragment UFS [snip] > The question of data size came about when I ran a backup of a directory > tree that is reportedly 76 GB. The Large DTF tape medium I'm using is > supposed to hold 108 GB at it's only compression ratio of 1:2.59. I ran > "tar -cvf /dev/sa0 /dir-tree". After some time, tar reported that it > had reached the end of the medium. Clearly 76 GB should fit on this > tape. I can't figure out what is happening here. Any ideas? The *best* compression rate you will get is 1:2.59. In the real world, you will get less because many files can not be compressed that much, if at all, by your tape hardware. You won't get much (if any) compression out of files that are already compressed such as mp3, jpg, mpeg, zip, etc. I have tape drives at work that "claim" to hold 20 GB compressed. I rarely get much more than the 10 GB native on them. I did the math on your tape and it will only hold about 42 GB native. So depending upon how much compression your actually getting, it's quite possible that 76 GB won't fit on one tape. HTH, Drew To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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