Date: Mon, 21 Dec 1998 12:17:22 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Dag-Erling Smorgrav <des@flood.ping.uio.no> Cc: Tim Jones <tjones@estinc.com>, "Jordan K. Hubbard" <jkh@zippy.cdrom.com>, Matt Jacob <mjacob@FreeBSD.ORG>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/sys mtio.h Message-ID: <199812212017.MAA47294@apollo.backplane.com> References: <82280.913951353@zippy.cdrom.com> <367A7E50.B0F5AA3B@estinc.com> <xzp7lvlfw17.fsf@flood.ping.uio.no>
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:> offer Quick File Access. This means that the user can say "Restore
:> mydatafile.dbf" and BRU will fast forward the tape to the appropriate
:> logical block address and restore the file. This means a file 2GB deep
:> on a DAT tape will restore in 30 seconds, instead of 45 minutes.
:
:Will this also speed up 'mt [fb]s[fr]'?
:
:DES
:--
:Dag-Erling Smorgrav - des@flood.ping.uio.no
No. fsf, fsr, bsf, bsr are implemented with SCSI commands which we
already support. Logical block seeking is requires the use of SCSI
commands that we do not (did not) support. Logical block seeking would
be a good thing, but not all tape drives can actually do it. DAT
drives usually can. I don't know about exabytes. Logical block seeking
is faster then reading because the tape drives are generally able to
fast forward and fast rewind to 'around' the right position, then figure
it out from there.
If you have several incrementals on the same tape restoring one file
will still take a little while - probably at least 5 to 10 minutes, but
you still win big time with a logical block seek capability.
-Matt
Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet
Communications & God knows what else.
<dillon@backplane.com> (Please include original email in any response)
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