"Poor" man's NAS

[Alma J Wetzker]

Net Llama! wrote:
> On Thu, 8 Jun 2006, Michael Hipp wrote:
> 
>>>From: "Alma J Wetzker" <almaw at ieee.org>
>>>
>>>I really doubt that the media and heads are any different between SCSI
>>>and IDE (That really is the choice, even though both now have serial
>>>options and speeds have improved.)  Is the rest of the drive different?
>>>   I don't know.
>>>
>>>The electronics, that I understand.  SCSI is still smart.  IDE is still
>>>rather stupid.  (IDE includes ATA and SATA)  IDE drives have all the
>>>useful stuff built into the controller.  The only do exactly what they
>>>are told, and only in that order.  SCSI, OTOH, takes all the commands,
>>>evaluates them and does them in the order that optimizes returning
>>>results based on what the drive mechanics need to do.  The performance
>>>difference is noticeable.
>>
>>I was under the impression that SATA was more like SCSI than good ol' PATA.
>>
>>The other side of the equation is in the CPU. I've seen charts of cpu load under heavy data transfer for IDE vs SCSI. The difference was dramatic (several x). (It gave the impression that IDE was a lot like a winmodem - all the real work done by the host cpu.) But again I had the impression that SATA was much more like SCSI in this regard.
> 
> 
> SATA is still a fairly immature technology, especially in Linux.  In terms
> of performance, I'd say its somewhere between PATA & SCSI.  In terms of
> features, its slowly edging towards parity with SCSI, but its not there
> yet, and there's a footnote that different drives have different features
> (and I don't just mean RPMs & capacity), and different SATA controllers
> also have different features.  So when you throw all those variables
> together, you end up with a fairly broad spectrum of performance &
> functionality for SATA.
> 
> And to make things interesting, there's a newcomer to the storage scene,
> SAS (serial attached SCSI).  Where SATA was kinda PATA getting mutated
> into SCSI, SAS is kinda SCSI getting mutated into SATA.

In terms of architecture, the world is moving to serial.

It is true that SATA is adding features, but SCSI is hardly standing 
still.  The SATA controller is still basically a floppy controller, 
usually for SCSI you can use something more sophisticated.

     -- Alma