>From S/390 point of view, usually, what you have is a hot swap set up so
that when a specific drive dies, the rest of the drives in the raid
group copy themselves over to the hot swaps and rebuild the lost data as
it goes.

You then fix the bad drive as soon as possible. S/390 DASD controllers
can, in some cases, actually place the call themselves, so your first
indication that a problem exists in the FE walking in with a new drawer.

In the Intel world, where much of this capability doesn't exist, if you
lose a drive from a raid set, you depend on how the hardware is setup
for the spare. If it spares just the bad drive, but not all of the
drives in the raid set, you may have other drives in the set go bad and
now you are without a spare. 

Just because data is on a RAID doesn't mean you stop taking backups;
your last line of defense is always going to be that dump to tape at
regular intervals.


Garry E. Ward
Senior Software Specialist
Maritz Research, Automotive Research Group
419-725-4123 

-----Original Message-----
From: Dennis Wicks [mailto:[EMAIL PROTECTED]] 
Sent: Monday, February 10, 2003 1:57 PM
To: [EMAIL PROTECTED]
Subject: raid question

Greetings;            (Posted to LINUX-390 and debian-s390 lists)

I came across an unsettling bit of info a while back.

I was told that if you lose one volume of a raid set you can replace
and the data will get rebuilt, but if you lose a second volume before
you get the first one rebuilt you will lose all the data --
irretrievably!

Is this true? Is there any reasonable way to get around it? Is there
a reasonable alternative to raid?

As always, Many TIA!
Dennis
--
Dennis G. Wicks             Systems Programmer      [EMAIL PROTECTED]
Communications Data Group   Tel: (217)355-7117  Fax: (217)351-6994
102 S. Duncan Rd.
Champaign, IL  61822


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