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RE: Soft-RAID and Hard-RAID?

RAID-O, also known as 'striping', is used because it improves speed and
allows one to incorporate multiple drives into a single volume (or multiple
volumes, actually). The price one pays for the extra speed is the added
risk of losing data because when one striped drive fails, all the data is
lost. This happens because the contents of each file are divided among the
striped drives.

RAID-1, also known as 'mirroring', is a configuration in which two or more
drives act as exact copies of each other. Whenever one writes a file to the
mirrored volumes, the file is written to all the disks in the array. The
advantage of RAID-1 is that when one drive fails, the data is safe on the
other drives. The price one pays for the extra safety of the data is the
need to allocate at least double the hard disk space for each file.

If you need extra speed AND safety, you may want to check out RAID-5 arrays
which use a type of striping AND mirroring and need only a fraction of the
hard disk space used by RAID-1. I'm sure someone else on the list can
explain how RAID-5 works better than I can, so I won't even try.

-Oliver




-----Original Message-----
From: Christoph Ewering [mailto:email@hidden]
Sent: Monday, April 29, 2002 3:14 AM
To: email@hidden
Subject: Soft-RAID and Hard-RAID?


Hello!

I?m running some Mac OS X Servers with a Sonnet ATA-Card and two drives
attached in RAID-1
configuration. (Soft-RAID that is included in Mac OS X).
After reading some really bad stories what?s happens when one drive of the
soft-RAID
fails, i want to switch to hard-RAID-1 solutions.

For myself I played around with the Soft-RAID in Mac OS X and was
disapointed that I only
see that one drive failed when I startup Disk Utility and select the
RAID-Volume. No other
warnings, NOTHING!!!

I expect to see a big warning at the login-screen that one drive failed!

After reconnecting the "failed" drive I had to rebuild the RAID by hand.
Startup Disk
Utility and rebuild it. But no data was lost.

I read some mails about drives in RAID-1 configs failing and than every data
was lost !!!!
Why should I use a RAID-1?

What I have found are only ATA-Cards that support RAID-0 but not RAID-1.
Where can I get an ATA-Card that supports RAID-1?

Thanks, bye,
Christoph
--
Dipl. Ing. Christoph Ewering
C & E Informationdienste GbR
Tel: +49 5254 806866
Fax: +49 5254 806864
Mobil: +49 173 5662661
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