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Date:      Sat, 13 Apr 1996 00:12:55 -0400
From:      "Jacob M. Parnas" <jparnas@jparnas.cybercom.net>
To:        scott@statsci.com
Cc:        Chris Stenton <jacs@gnome.co.uk>, hardware@freebsd.org
Subject:   Re: Micropolis 1991 AV 9GB Drive 
Message-ID:  <199604130412.AAA00142@jparnas.cybercom.net>
In-Reply-To: Your message of Fri, 12 Apr 1996 12:05:36 PDT. <m0u7oA5-000r3uC@main.statsci.com> 

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In message <m0u7oA5-000r3uC@main.statsci.com>you write:
>Chris Stenton <jacs@gnome.co.uk> wrote:
>
>> Is there a better 9GB drive I should be going for ... any advice would 
>> be appreciated. 
>

9 GB drives have advantages and disadvantages.  The main advantage is 
especially for large servers,   You can get more disk space on it.  I 
think most of the other problems aren't too bad.  You should be doing nightly
backups on data you'd really miss losing.  Last I checked, the 4.3 gig drives
were a bit faster and used less power and may be smaller (not sure about the 
latter).  Also, more disks running in parallel is an advantage as is leaving
some physical space and controller slots available for future breakthroughs.
If one can distribute the load over a bunch of disks, one can speed things
up as one can if one makes the disks.

If your working on an existing system, its really useful to have a feeling
for where their bottleneck is in their system, be it cpupower, video card,
disk, disk controller, disk type, disk controller type, etc.  Use tools
like periodic ps aux or ps vax into a file during problem times in the day.
Read a good book on Unix performance tuning. (I think there's one bye Mike
Loukides (an O'reilly book).  You may need more memory or cache.  You may 
need a faster network or file server or to have the disk local vs. via
file-server.  You need to figure out where the problem is.  An archive source
disk may be fine for something where it would be bad as a "one disk does it
all" disk.  

I think some OS's can combine disks into virtual bigger disks for large
filesystems.  To be honest, I don't know if BSDI can do that.  But if not,
and you might have some large space for big file or database.

Also, don't be shy about using the excellent program gzip/gunzip which can
be used recuseively with the -r.  It is great for saving space.  Most source
code can be made distclean to almost its original size and then gzip -r it
for storage.  Big things like X windows source can easily taped and removed
from disks.

Finally, I've heard, but not tested, that having extra controllers (fewer disks
per controller).  I'd try to get access to a lot of systems or get eval units
or 30 day net controllers and calculate good transfer rates for a disk, etc.

Hope that helps,

Jacob



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