[K12OSN] Are fast disks really that important and why?

john lists.john at gmail.com
Fri Jun 1 15:29:28 UTC 2007

Thanks Sudev,

I think you're probably right.


On 5/31/07, Sudev Barar <sbarar at gmail.com> wrote:
> On 01/06/07, Paul VanGundy <Paul.Vangundy at webex.com> wrote:
> > There's definitely a better way to read disk I/O. Try using 'iostat -k
> > 2' and watch as every two seconds you get a read of your disk I/O as
> > well as what your cpu utilization is. Pay attention to %iowait as you
> > look at it also.
> >
> Run:
> #hdparm -tT /dev/sda (for scsi and sata)
> #hdparm -tT /dev/hsa (for PATA ide)
> I find the figures returned for cached and buffered disk reads very
> much in line with my fast/slow experience in running a LTSP network
> with 35 clients. Money allowing I would always go for raid1 scsi. With
> cost of one disk and controller already in place one more disk does
> not take that much extra.
> As already explained the scsi drives requeue or do parallel queuing to
> prioritise near by data to the head location resulting in faster user
> experience. In PATA/SATA queue is processed one by one resulting in
> large head moments where head may have to travel back and forth as
> queue are not processed in parallel. This is my understanding till
> now.
> However newer sata's are good and i would say if money is constrain
> then go for raid1 sata's. Why raid1? Avoid the misery of disk going
> bad on you. It is worth it.
> --
> Regards,
> Sudev Barar
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