Re: RX2800 sporadic disk I/O slowdowns

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

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

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.

>
Yes.
>
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.

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.
And with a power outage they have hours to get power back and get the
data written (I believe 72 hours battery power is common).
Arne