SATA question

Andy Burns fedora at adslpipe.co.uk
Wed Feb 1 12:54:26 UTC 2006


Ivan Gyurdiev wrote:

> Well, I think this is a SATA drive..
> WDC WD2000JS-55MHB0

Yes, some SATA drives, are re-designed from the PATA drives, 
incorporating a SATA/PATA bridge on the drive, I think yours is similar 
to mine, with native SATA

Of course you can also buy external SATA/PATA convertors, but I wasn't 
expecting you to be using one of those.

> It's nice to know my SATA II drive is so much superior :)

If the rpm, number of platters, and data encoding stay the same, so will 
the performance, broadly speaking, 8MB or 16MB of cache will only have 
an effect if you're doing reading that fits a certain pattern, and as 
we've seen the physical disk couldn't even half fill an ATA133 interface 
(let alone SATA, or SATA II) only cache reads can do that.

> How does NCQ make a difference?

It lets the o/s make several read requests to the drive in parallel, 
then the drive re-orders them according to where it *know* the physical 
heads are to minimize seek time, and maximize throughput. like SCSI has 
done for a long time.

Remember they head/cylinder/sector numbers you see from SATA/PATA disks 
are basically *lies* with LBA so the o/s can't know this.

> Also, jgarzik's webpage says: "Nvidia has released docs on nforce4 under 
> NDA".
> Do you know if there's work in progress to implement NCQ for that chipset?

Sorry I don't have (or know about) nForce chipset, my Intel mobo 
supports SATA II's 3Gb/s speed, but not the NCQ.





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