[THIN] Re: new Dell 1650 questions?

  • From: Barry Flanagan <barry.flanagan@xxxxxxxxxx>
  • To: "'thin@xxxxxxxxxxxxx'" <thin@xxxxxxxxxxxxx>
  • Date: Mon, 28 Oct 2002 11:13:47 -0500

In my experience, you do not need the fastest CPU available. I rarely see a
CPU bottleneck anymore. The processor power available today is usually far
greater than whats required (not always, but in most cases). The bottleneck
I see the most these days is the one most often ignored, DISK. You can save
a great deal of money by using a slightly slower CPU and investing in other
subsystems that are more likely to be a bottleneck. 
I see many customers using RAID5. While RAID 5 provides cost effective fault
tolerance, it has the worst write performance. This can impact a write
intensive operation like paging.  Once the disk is a bottleneck, the memory
subsystem does not have fast access to its page file, and disk is a
bottleneck. 
I recommend 2 RAID 1 mirrored sets, one for OS and Apps, one for the page
file (and spooler in some instances). While RAID 1 has only marginally
better write performance than RAID 5, separating the disk spindles by
function improves performance a great deal while still providing fault
tolerance. Ideally, you want a RAID controller and mirrored set for OS,
Apps, and Pagefile (this is recommended in the Advanced Concepts Guide).I
have seen a few customer use 2 RAID controllers and two mirrored sets, but
have yet to see one with the budget for three. 
You need a RAID controller with at least 64 MB of Cache that is configured
for 50% Write/50% Read cache.  Writing to RAM in a RAID cache is up 150,000
times faster than writing to physical disk. I had a customer have a
performance issue above 20 users on a QUAD Processor XEON with 2 GB of RAM.
Each time a user started a session with autocreated printers, disk
utilization shot to 100% and network traffic dropped to 0. Upgrading to a
RAID controller to 64 MB of cache and enabling it to use both read and write
cache allowed them to get their goal of 70 users without a problem.
Microsoft recommends this in Q307931. Microsoft updated the Q article as a
result of this customers findings.

BTW, has anyone priced out QikDrives and Qik Cache from Platypus
Technologies lately. Their Solid State drives can greatly improves
performance and scalability, but the last time I looked they were incredibly
expensive.



Thanx,

Barry Flanagan


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