large file cp or diff error

On 2014-01-18 06:26, ThomasZMitchell wrote:

> Wait – disabling write cache does not make the disk slower – it runs
> at the same speed, regardless. Having a write cache enabled increases
> the user’s perception of quickness because you click on save and the
> system is ready for a new activity even though your 50 MB file is not
> quite written to disk, yet. Well, you know what I mean.

Yes, it is slower, specially under high system load. Continuous write
speed of one file is about the same, yes, but not of multiple and small
write operations. The disk can not optimize head movements, and waiting
for them makes overall speed slower.

The kernel can try to do such optimizations as well, but as the hard
disk hides how are sectors really distributed, it can’t do this to well.

> I have read articles on the web about this. Many comments such as ‘I
> want the performance,’ and ‘I’ve never had an issue.’ But other
> comments exhorting us to disable to prevent data loss. I disable.

It is your choice, of course. :slight_smile:

I’m not running any mission critical system that may need totally
reliable disk commits. If I were, I would buy battery backed controllers
instead, and still use write cache.

Cheers / Saludos,

Carlos E. R.
(from 12.3 x86_64 “Dartmouth” at Telcontar)