Sujet : Re: RX2800 sporadic disk I/O slowdowns
De : ldo (at) *nospam* nz.invalid (Lawrence D'Oliveiro)
Groupes : comp.os.vmsDate : 21. Oct 2024, 02:10:56
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <vf49n0$kvdg$1@dont-email.me>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
User-Agent : Pan/0.160 (Toresk; )
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.
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.