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system I/O rate reported high by MeasureWare on a couple disks

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Stephen Serbe
Occasional Advisor

system I/O rate reported high by MeasureWare on a couple disks

N-class 8-way 550Mhz w/12 Gbyte RAM
These disks show high queuing, and their I/O as reported by MeasureWare is attributed to System I/O, instead of physical read or physical write I/O. MeasureWare help is non-informative. Yes, they are root disks, internal to N mirrored across SCSI, but only have 1 Gbyte swap, we have 8Gb swap on XP256, and we do not swap, a high page rate might be 1-2 second PEAK! How do I determine what workload (processes) are causing this and/or what is the general concensus of the source of "system I/O" Otherwise, it does not appear to be typcially a big factor. Thanks.
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S.K. Chan
Honored Contributor
Solution

Re: system I/O rate reported high by MeasureWare on a couple disks

High system I/O can be due to kernel using these resources to manage the memory and processes between swap device and physical memory. This might/might-not impact your system performance to a "noticeable" level. Do check if your pseudo-swap is ON, though we know it's should be ON by default. You can use Glance and go through each processes and check for it's "wait-state", the suspected ones will have "system io" as the "wait-state".
Meanwhile I'm attaching a writeup (fr Technical DB) about swap. I'm used to configuring at least a 1:1 ratio with physical memory for my swap, if disk space is not a problem you might want to do that.