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From: weghorst@nilenet.com (Mark Weghorst)
Newsgroups: comp.databases.oracle.server
Subject: Re: Caching RAID controllers versus non-cached RAID
Date: 7 Jul 1998 17:33:56 GMT
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MotoX (rat@tat.a-tat.com) wrote:
: I'd only ever use a 'write-through' cache, or a system with heavy, localised
: power supplies and much redundancy (like EMC Symmetrix) for the cache
: subsystem. If that caches goes down, your database is potentially corrupted.

That a very valid concern.  I wouldn't use any array that didn't have a
battery backup for the cache.  For example on the Nike arrays (Data
General and HP 10/20/30), there is a battery option that will write the
contents of the cache out to a reserved area on the disk.  When the array
is powered back up, it reads the contents of the cache flush area on the
disk and applies the changes before the array is brought on line.  

By contrast the 12H Autoraid array merely holds the information in
battery-protected memory until the array comes back on, and then commits
the writes.  The batteries should last about a week without power.

I'm not sure about the Sun A5000, but all of the tech docs are on
http://docs.sun.com

-Mark Weghorst