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Re: [K12OSN] Sanity check needed before rollout



On Tuesday 29 May 2007 22:29, Les Mikesell wrote:
> john wrote:
> > Why does disk speed matter so much? Aren't most operations on a file
> > server fairly small scale i/o once or twice a session i.e. opening a
> > saved document, and writing a saved document.?
>
> The problem on a multi user machine is that every user wants the disk
> head to be in a different place at the same time so seek time is often
> more important than transfer rates. Consider what happens when everyone
> is using a browser and every page and image each user loads is being
> cached in their home directories.  Scsi disks/controllers can typically
> take a bunch of commands at once and queue them up while IDE and most
> SATA's can only do one comand at a time, waiting for CPU intervention at
> each step.
>

The behavior ("Scsi disks/controllers can typically take a bunch of commands 
at once and queue them up..."), is known as "elevator seeking" and is a huge 
advantage of SCSI over SATA.

-- 
        "History doesn't repeat itself; at best it rhymes."
                        - Mark Twain

| John Lucas                          MrJohnLucas gmail com               |
| St. Thomas, VI 00802                http://mrjohnlucas.googlepages.com/ |
| 18.3°N, 65°W                        AST (UTC-4)                         |


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