Re: [squid-users] Sizing a pretty Large Squid Install

Chemolli Francesco (USI) wrote:

> Yes.
> The idea is to exploit (if possible) elevator optimization in moving
> the drive heads, which requires having multiple outstanding
> requests on the same drive. Diskd only has one active disk operation
> at any given moment AFAIK.

Not only elevator optimization, but also I/O queues to make sure there
is another disk I/O request pending immediately when the first have
completed. A single process cannot do this (on reads) as it has to wait
for the first to complete before it can schedule the next I/O operation.

> Probably mostly irrelevant under normal conditions, but it can help
> decrease consistency checks and crash recovering.

It should help a lot in decreasing total I/O latency times for cache
hits.

Does not help very much for consistency checks and/or crash recovery.
Those are still limited by Squids single main process only capable of
doing one small fragment at a time..

--
Henrik