Re: RX2800 sporadic disk I/O slowdowns

On Sat, 19 Oct 2024 21:31:51 -0400, Arne Vajhøj wrote:

On 10/19/2024 9:25 PM, Lawrence D'Oliveiro wrote:

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On Sat, 19 Oct 2024 21:22:08 -0400, Arne Vajhøj wrote:

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On 10/19/2024 9:04 PM, Lawrence D'Oliveiro wrote:

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Here’s another question: why does a disk controller need a battery-

backed-

up cache? Or indeed any cache at all?

>
Better performance.

 
Think about it: the OS already has a filesystem cache in main RAM. That
runs at main RAM speeds. Whereas the disk controller is connected
through an interface to the CPU suitable only for disk I/O speeds. So
any disk controller cache is on the wrong side of that interface.

 
That cache is toast if the system crashes. So applications
that need to be sure data are written bypass that.

You can say the same for applications keeping data in their own RAM
buffers. It’s a meaningless objection.