Re: [squid-users] DiskD worthwhile for single-disk cache?

Adrian Chadd wrote:
>
> On Sun, Apr 08, 2001, Steve Snyder wrote:
> > Having read the Squid doc on DiskD, I am left with the impression that the
> > primary (only?) benefit is to multi-disk configurations of Squid. True?
>
> Kind of. diskd is designed to work around the problem of blocking IO
> in a unix process. asyncufs gets around this by using threads to complete
> disk IO. diskd uses external processes to complete disk IO.

In case it was not clear. asyncronous I/O (diskd/aufs) is beneficial for
single drive configurations with "higher" request loads, in many cases
allowing you to push about 100% more I/O thru the drive before latency
creeps up too high.

For multiple drive configurations it is almost a requirement to be able
to use the I/O capacity of the extra drives. Without it a multiple disk
configuration is effectively limited to almost the speed of a single
disk configuration. With asyncronous I/O the disk I/O scales quite well
(at least for the first few drives, other limits gets very apparent when
you have more than ~3 drives)

--
Henrik Nordstrom
Squid Hacker