Path: utzoo!attcan!uunet!virtech!cpcahil
From: cpcahil@virtech.uucp (Conor P. Cahill)
Newsgroups: comp.unix.i386
Subject: Re: Tape backup performance on 386 ISA/EISA systems
Keywords: tape, performance, 386
Message-ID: <1990May31.131341.15453@virtech.uucp>
Date: 31 May 90 13:13:41 GMT
References: <1990May25.123302.26061@virtech.uucp> <1990May26..841@rdk386.uucp> <1990May30.132457.6117@virtech.uucp> <1060@sixhub.UUCP>
Reply-To: cpcahil@virtech.UUCP (Conor P. Cahill)
Organization: Virtual Technologies Inc., Sterling VA
Lines: 40

In article <1060@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes:
>In article <1990May30.132457.6117@virtech.uucp> cpcahil@virtech.UUCP (Conor P. Cahill) writes:
>
>| 2. The performance of the disk due to optimizations will probably have
>| little performance effect on the overall perforance on the tape write, since
>| the tape write is the limiting factor.
>
>  I'm sorry, this is just totally wrong. You must never have had a
>fragmented disk. I have seen transfer rates as low as 300kBytes/sec with
>a fragmented disk and streaming tape which ran in fits and starts. I see
>about 4MB overall (from the time I hit return to the time the tape is
>rewound) on a non-fragmented f/s. At least with standard Xenix and UNIX
>f/s there is a huge gain for backup.

300kBytes/sec = 18MB/min which is much faster than any tape backup that
I have seen/heard was available for a 386, so there still wouldn't be enough
gain in the backup to make that much of a difference.

If you still disagree, run the test I mentioned on a non-optimized disk
and then run the same test after the disk has been optimized and
report the results.  I had one other person do that and the difference
was less than 10% which would be expected anyway due to the differences
in file system layout (like zillions of 1 byte files vs 1 zillion byte file).

Note that I am not saying that it has no effect.  I am just saying that
it will not change the results for the test that I specified from 4MB/min
to 6 or 8 MB/min.

>  I have not been able to show degradation in performance due to
>fragmentation of the ufa type filesystem on V.4, so perhaps this will
>all go away in a year or so.

You probably won't see that much difference under one of the FFS's available
for 386 unix boxes (like 386/ix, SCO Unix, ESIX).


-- 
Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.,
uunet!virtech!cpcahil                           46030 Manekin Plaza, Suite 160
                                                Sterling, VA 22170