Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!umich!samsung!cs.utexas.edu!uunet!crdgw1!sixhub!davidsen
From: davidsen@sixhub.UUCP (Wm E. Davidsen Jr)
Newsgroups: comp.unix.i386
Subject: Re: Tape backup performance on 386 ISA/EISA systems
Keywords: tape, performance, 386
Message-ID: <1125@sixhub.UUCP>
Date: 10 Jun 90 03:36:33 GMT
References: <1990May25.123302.26061@virtech.uucp> <1990May26..841@rdk386.uucp> <1060@sixhub.UUCP> <1990May31.155113.8383@ico.isc.com> <1990Jun8.223358.27138@murphy.com>
Reply-To: davidsen@sixhub.UUCP (bill davidsen)
Organization: *IX Public Access UNIX, Schenectady NY
Lines: 32

In article <1990Jun8.223358.27138@murphy.com> peterg@murphy.com (Peter Gutmann) writes:

| All of the tools required for disk de-fragmenting exist in the base
| distribution of UNIX. All it requires are three simple steps,
| 
| 1) create a backup of the device using your favorite backup utility 
|    (such as tar or cpio). Don't use dump or any other utility which
|    creates a "image" of the file system.
| 
| 2) erase the contents of the devices that has been backed up
|    in step one (above).
| 
| 3) restore the device from the backup made above.
| 
| what this accomplishes is that the device has all of the blocks
| in the file system moved to the free list. then reallocated sequentially
| from the backup.

  If you do step 2 via mkfs, or if you have a filesystems which uses a
bitmap, this is true. However, you said freelist, and in that case you
had better do an fsck with the -s option to order the freelist, or you
don't gain much.

  Since dump can be used between diferent size filesystems (given enough
room on the 2nd f/s) I believe that the information is logical rather
than physical, and that a restore defragments the disk. At least on this
(Xenix) system. A physical dump doesn't (dd /dev/rawdisk /dev/tape) type.
-- 
bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
    sysop *IX BBS and Public Access UNIX
    moderator of comp.binaries.ibm.pc and 80386 mailing list
"Stupidity, like virtue, is its own reward" -me