Subject: Re: Raid/System setup recommendations
To: None <>
From: Jon Lindgren <>
List: netbsd-users
Date: 01/31/2001 09:33:01
On Wed, 31 Jan 2001, Thomas Michael Wanka wrote:

> Hi,
> I recently bought a cheap 7 disc UW case with 7 4,5GB drives. Is it 
> reasonable to get a cheap DPT Raid controller or should I prefer 
> softwareraid? Should I expect performance advantages of either 
> solution and would a cache on the controller be of any good and 
> does softwareraid a good job when it comes to hot swap of drives? 

Not to knock raidframe at all (I think it's an excellent piece of
functionality), but I've had much better luck with hardware raid
devices.  I've found hotswap under NetBSD (at least under some NCR
chips and Adaptec 2940UW) to work, but not reliably enough for me to sleep
well at night.  For a production system, I'd personally recommend a
hardware based approach.

I am a big fan of CMD's SCSI->SCSI RAID boxes, but they've grown pretty
hard to find (and expensive, unfortunately).  Using these, NetBSD sees one
big hard disk, and leaves the hotswap/hotspare/magic to the CMD.  My mail
server runs very well using one.  I sleep well at night.

Again - I don't mean to knock raidframe at all - but I've personally
experienced a few gotchas, and I've seen some quirks, which I just can't
do in a production system.  It'd be real nice to use raidframe, and good
things come to those who wait, so I'm waiting ;-)

> This is a production system, so I am restricted in my possibilities to 
> test.
> I still need one Linux machine to run Win32 under vmware, I thought 
> I could mount parts of the Raid by NFS, specially the virtual disk 
> files used for vmware. Does this sound stupid to anyone, or is there 
> a better solution someone can recommend?
> I remember I had problems some years ago when I tried to boot 
> from high SCSI ids (8-16) is there something known I should 
> consider?

The only thing to make sure of is that 1) either your kernel knows
specifically about which disk the root fs is on, or 2) your disks are
arranged such that sd0a is the disk your root fs is on.  For example,
booting from SCSI ID 2 with a disk also installed on ID 1 has caused me
problems in the past (that was with a 1.3 release... I've not tried it
recently, so there may be more magic (tm) these days).

Definitely experiment with raidframe if you can.  It is a rather cool
piece of functionality, definitely a bunch cheaper than a hardware RAID,
and also [probably] has a number of people testing it all the
time.  My expierence is that it's not as fast as hardware, but unless
you're looking to store gobs of info at lightspeed, it'll most likely fit
in quite well.

Just my $0.02.  Apply grain of salt.  etc...

Hope this helps,

 - The opinions expressed are not necesarily those of my employer.
 - latest Health news for 12/4/2000 at 2:10 p.m.:
    Tobacco firm backs lung cancer test: Spaz the cat will never again
    want for medication to relieve his constipation.