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Date:      Tue, 14 Jan 2003 09:16:22 -0500
From:      Bill Moran <wmoran@potentialtech.com>
To:        Ion-Mihai Tetcu <itetcu2@xnet.ro>
Cc:        questions@freebsd.org
Subject:   Re: Vinum over (2xSCSI, 1xIDE) ?
Message-ID:  <3E241BB6.5080304@potentialtech.com>
References:  <5.1.0.14.0.20030114123344.036b0b68@pop31.xnet.ro>

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Ion-Mihai Tetcu wrote:
> Hi,
> 
> I have to setup a database (MySQL) server this days.
> The machine will be a AthlonXP 2000+, 1G RAM, 2x Cheetah X15 36LP series 
> drive of 18GB.
> And I could spare a 20G ATA100 IDE drive.
> 
> I have no experience with vinum, so i want to ask you if it is a good 
> ideea to add the IDE drive. I was thinking to use it as a backup drive 
> in case the SCSI controller fail. I'm courios about what impact will 
> have on the performance of the system and as the server will have to 
> enter in production in a few days I do not have the time to play with.

I'm not going to take the time to research the specs on each of those
drives.  However, if the ATA drive is slower than the others, and you
configure the three in a striping configuration, the total speed of
the array will be limited by the slowest drive.  (The same would be
true of a mirroring config, but you don't generally do that with 3
drives)
If you config them as concatenated, or with different partitions, the
speed will depend on which drive is being accessed.

So the answer is: whether or not it's a good idea depends on how you
configure it.  If you configure the ATA as temp space, and the Cheetahs
as database storage space, you'll probably see better performance than
if both were on one drive, since writing to both ATA & SCSI simultaneously
should go faster than trying to write temp and data to one drive at
once.  However, even this depends on your motherboard and controller, so
your actual performance is going to depend.  Unless someone else has used
your exact config and done benchmarks, there's no way to be 100% sure.

-- 
Bill Moran
Potential Technologies
http://www.potentialtech.com


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