Jos Chrispijn wrote:

>> prad wrote:
>> i've heard scsi hard drives are really good.
>> i've also seen at least one site which claims that ide easily
>> outperform scsi.
> Prad,
> Have a look at this URL:

While I found this interesting, I also felt some data points could have been 
added. I believe these have some bearing for decision making as they better 
define the choice based upon what task, or purpose, the system is being called 
upon to perform.

The concept that SATA subsystems will tend to consume more CPU cycles because 
SCSI controllers have onboard processors is somewhat nullified when considering 
controllers such as the Areca 1210 and the 3Ware type of products.

One historical difference wrt to desktop type machines that manufacturers stuck 
RAID controllers on in order to have marketing buzzwords is that they were 
essentially useless for performance purposes. They were all hung off the 
Southbridge and were hamstrung by the maximum bus throughput between the South 
and North Bridge.

The PCI-X bus was designed for server boards so this kind of bottleneck would 
not hamper performance. With the advent of PCI-E 8x slots and controllers this 
same situation has come to the SATA arena.

The next consideration will be purpose: is the box going to be used as an 
inexpensive disk-to-disk NAS, file serving, or some other generic mode where 
size and high sequential throughput are primary concerns. Or is it called upon 
to perform lots of quick random selections of data such as a multithreaded 
database server?

One item that gets lost in the RAID discussion is that, while sequential r/w 
performance generally goes up as you add more drives to the array, latency also 
increases. The additional latencies introduced may not matter as much to the 
sequential throughput scenario but will have more impact on the database server 

So the with sequential file serving it is OK to use 8-9ms seek time drives as 
we are more interested in sequential throughput and not as concerned with 
latency. Here SATA is probably a good match.

For the high performance database server application you are going to want to 
use 3-4ms seek time drives to keep latencies under control while adding drives 
to the array. These are going to be the more expensive high RPM SAS and Fibre 
Channel drives. If you're already spending $40K/CPU for Oracle what's a few 
more dollars for Fibre Channel?  :-)

Can't wait for SSD devices to replace this.

Just my $.02 here - I thought I'd toss this out in case anyone might find it 


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