Re: File system compression, not at the block layer

From: Paul Jackson
Date: Fri Apr 23 2004 - 18:37:49 EST

> If you want to have fast disks, then you should do what I
> suggested to Digital 20 years ago when they had ST-506
> interfaces and SCSI was available only from third-parties.
> It was called "striping" (I'm serious!).

That gets your bandwidth up, but does nothing for latency.

Depending on your workload, that may or may not be critical.

As a former SGI employee noted:

"Money can buy bandwidth, but latency is forever" -- John Mashey

To get latency down, you need fast rotating disks and short strokes
(waste most of the disk on little used data, or on nothing at all).
And even that won't get you much faster than 20 years ago.

That, or lots of main memory, or if the data is pretty much
read-only, perhaps some complicated data duplication.

But we're not in such bad shape there - folks have been dealing
with that speed difference for at least 20 years ;).

It's the speed difference between the processor and main memory
that's more challenging now - as it approaches speed differences
we once saw between processor and disk.

To heck with disk compression - it's time for main memory compression.

I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@xxxxxxx> 1.650.933.1373
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