Re: What is a Block Device?

How does that differ from a JFS?

• Dc

Andre Whittick Nasser wrote:

> Hi !
>
> Well, the difference between a block and a raw(or character) device is that
> a block device uses OS buffer cache and is more specific to physical devices
> that work with blocks (like disks). Raw devices bypass any kind of buffer.
> If you go to /dev and list the pseudofiles with "ls -l | more", you'll find
> a "c" before raw devices and a"b" before block devices.
> At first, it would have a better performance because of the caching effect.
> And if the bock size is big, you'll feel the "spatial locality" working.
> That is, in one read, you will bring along more data that is physically
> close to that you originally wanted. And according to statistics, this other
> data will very likely be used in the near future.
> Its maintenace difficulties are the same.
>
> Chakravarthy KM Nalamotu escreveu na mensagem
> <83e1ja$au0$1_at_news.hawaii.edu>...
> >Hello Oracle Users,
> >According to Oracle8 tuning manual a block device gives
> >better performance than a raw device and a UNIX file
> >system when large block sizes are used.
> >I know what a raw device is and what a UNIX file system is.
> >What is a Block Device? How does it work? Does it have
> >maintenance difficulties similar to raw device?
> >Thank you for your responses.
> > Kittu.
> >

Received on Sat Dec 18 1999 - 19:59:34 CST