Re: RX2800 sporadic disk I/O slowdowns

On Sun, 20 Oct 2024 21:17:06 -0400, Arne Vajhøj wrote:

On 10/20/2024 9:10 PM, Lawrence D'Oliveiro wrote:

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On Sun, 20 Oct 2024 20:32:41 -0400, Arne Vajhøj wrote:

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On 10/20/2024 8:28 PM, Lawrence D'Oliveiro wrote:

Transaction resilience is a standard thing with databases (and
journalling filesystems) going back decades.

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Yes.
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But they can't do miracles.

 
They can ensure, to a high degree of confidence, that the on-disk
structure is consistent. That is to say, each transaction is either
recorded as completed or not recorded at all, nothing in-between.

 
Only if it can rely on a successful write not being lost.

In other words, that the disk controller is not lying to you when it says
a write has completed?

To be sure to come up ok after a system crash it is either write to
plates or write to a cache that will survive the system crash (raid
controller cache with battery backup).

 
Unfortunately, that controller cache can’t guarantee any of these
things: it can’t do miracles either, all it does is add another point
of failure.

 
Yes - it can.
 
It is not impacted by a system crash.

Now you are really starting to sound like a believer in miracles ...