RAID autodetect?

[hewitt_tech]

When I worked for Compaq in their UNIX support group (my specialty was file 
systems), our engineers noticed a pronounced difference in performance 
between for example RAID 5 and disks set up as JBOD. The JBOD disks were 
definitely faster. Of course for high performance systems we used fibre 
channel and logical volume manager (Veritas) on top of our RAID arrays. The 
big advantage of the Veritas software was that we could spread our I/O load 
across RAID controllers and some customers had huge arrays consisting of 
hundreds of disks. Tru64 UNIX was heavily modified for the V5.x versions to 
allow arbitrarily large numbers of disk devices to be addressed and managed.

-Alex

----- Original Message ----- 
From: "Bill McGonigle" <bill at bfccomputing.com>
To: "hewitt_tech" <hewitt_tech at comcast.net>
Cc: "GNHLUG" <gnhlug-discuss at mail.gnhlug.org>
Sent: Friday, November 25, 2005 9:34 AM
Subject: Re: RAID autodetect?


> On Nov 25, 2005, at 06:59, hewitt_tech wrote:
>
>>  you might have quite a difficult time getting the configuration correct 
>> so that you could recover your system. I thought that hardware RAID 
>> arrays (usually SCSI) didn't have this problem since the platform 
>> software only sees a disk or disks and not the underlying RAID hardware.
>
> Autodetect should help with that because you don't need the .conf files - 
> a copy of the RAID configuration is stored in some sort of RAID header, 
> which makes recovery easier.  The Fedora recovery CD, for instance, will 
> detect and understand them.
>
> Hardware RAID is certainly easier to configure and you can do things like 
> fiberchannel arrays which support things Linux doesn't (fiber channel 
> networking, IDE hotswap, for instance).  But... they're typically slower 
> (the hardware geeks on the PostgreSQL list claim 5x performance for a 
> Linux RAID mirror over an Adaptec SCSI RAID controller) and if you have a 
> unique RAID board burn out you're totally screwed until you can purchase a 
> new, identical, one (onsite spares required for critical apps) .   With 
> Linux RAID your RAID pack is compatible with any generic PC.
>
> -Bill
> -----
> Bill McGonigle, Owner           Work: 603.448.4440
> BFC Computing, LLC              Home: 603.448.1668
> bill at bfccomputing.com           Mobile: 603.252.2606
> http://www.bfccomputing.com/    Pager: 603.442.1833
> Jabber: flowerpt at gmail.com      Text: bill+text at bfccomputing.com
> Blog: http://blog.bfccomputing.com/
>
>