Re: [IMail Forum] New Server Specs

Thu, 23 Feb 2006 18:34:12 -0800

The biggest mistake that people make when reading charts of RAID performance is assuming that this is done from the perspective of real world installations.  They for the most part are not.  The idea of comparing a 4 disk RAID 10 array to a 3 disk RAID 5 array is not a fair comparison.  They are roughly similar overall when using 4 drives on each, though RAID 5 does a bit better on reads.  My servers fit 6 drives in them, so the real world scenario that matters is what is the best performing fault tolerant RAID type that I can run with 6 drives.  The answer is RAID 5.  RAID 10, 0+1, 1E, or whatever you wish to call it, can only scale to the efficiency of half the number of disks, and with 6 drives, that is only 3 disks worth of performance (roughly of course), while you can have all 6 drives working on tasks in RAID 5.  Sure there's overhead to RAID 5 with writing parity data, but you are doing that with 6 disks instead of 3.  For reads, it can be up to 5 disks serving the reads instead of 3 again.  No doubt about it, RAID 5 is better for such things.

Regarding how far to scale, I doubt that a RAID 5 array with just 3 disks would have any issues handling 100,000 E-mail's a day.

Matt



Darin Cox wrote:
Nope.  Note that twice as much data is written with 0+1, compared to only N/(N-1) with 5.  So data transfer would be higher with 5.
 
RAID 5 is less fault tolerant, uses fewer disks, and is generally higher performing, as portions of the data can be read/written from all disks in the array at the same time.

Darin.
 
 
----- Original Message -----
Sent: Thursday, February 23, 2006 7:36 PM
Subject: RE: [IMail Forum] New Server Specs

Isn’t their chart wrong?  It shows RAID 5 as “very high” and “very high” while RAID 0+1 is only “high” and “very high” which would seem to indicate RAID 5 is better and uses less disks.  Looks like a typo ???

 

From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Christopher Checca
Sent: Thursday, February 23, 2006 4:32 PM
To: [email protected]
Subject: RE: [IMail Forum] New Server Specs

 

Here’s a good high level view of RAID levels…   http://www.raidweb.com/whatis.html

 

I use their 8 drive SATA SCSI interface units with RAID 0+1 with my SQL servers and RS/6000 AIX servers.   Performance is two to three times any DELL or IBM raid arrays I’ve used.

 

 

Please note in real world usage I’ve seen RAID 0+1 well out run any RAID 10 array.

Christopher Checca
Packard Transport, Inc.
IT Department
24021 South Municipal Dr
PO Box 380
Channahon, IL.  60410
815 467 9260
815 467 6939 Fax
[EMAIL PROTECTED]
www.packardtransport.com

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Jim F.
Sent: Thursday, February 23, 2006 2:13 PM
To: [email protected]
Subject: [IMail Forum] New Server Specs

 

Hello All:

 

I haven't gotten any responses to any of my other questions that I've sent to the group, hopefully this one will.

 

I'm trying to spec out a new server and had a question for the group in regard to HDD configuration.  What kind of RAID setup works best on a mid-size Imail installation?  Is RAID-1 acceptable or is RAID-5 recommended? Also, would 15K RPM disks make a huge difference as opposed to 10K RPM disks?

 

Thanks,

Jim Frasch

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