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rp3410/rp3440 scsi upgrade

 
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Derek Whigham_1
Trusted Contributor

rp3410/rp3440 scsi upgrade

I have 3 servers 2 rp3410 and 1 rp3440 , They have 2xUltra 320 15k Disks installed,

We are hitting an I/O bottleneck which seams to be related to the fact that these machines only have Ultra 160 SCSI Contollers. I have asked HP for an upgrade , But they are saying that I can only have an Ultra 320 contoller with PA8900 CPU module and Not PA8800, I cannot get an explaination why , Does anybody know.
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Bill Hassell
Honored Contributor
Solution

Re: rp3410/rp3440 scsi upgrade

The explanation is that HP chose to design the Ultra 320 controller to work with the newer 8900 series of computers. Without accurate details, I can guess that the older architecture (memory bus, I/O channel adapters, etc) can't keep up with the 320 card, especially when the system is fully loaded with 320 cards and high speed disks.

It's easy to assume that going from 160 to 320 will double the throughput, and improve overall performance. However, the interface speed is only a small part of the total I/O throughput. If the disk has very limited cache space (JBOD disks usually have just a few megs), then seek time and rotation rate are much more important. And of course, the access patterns caused by your application programs can rfeduce the overall throughput to much less than 160 SCSI performance.

And as stated many times here in the Forums, there are a lot of bad applications, bad SQL code, and simply poor design (a very large disk for everything). Rather than hide poor design with a faster I/O card, you may find 5 x to 10x improvement by examining the data layout and look at additional smaller disks to separate conflicting access. top and sar will help with the analysis but you really need to purchase Glance to see the big picture.


Bill Hassell, sysadmin
Derek Whigham_1
Trusted Contributor

Re: rp3410/rp3440 scsi upgrade

Used an external array
Divide and Conquer