Hardware for serving lot's of Raster

[Shawn Wallbridge]

On 20-Nov-05, at 11:07 PM, Ken Lord wrote:

> Hi Shoaib, Ed,

<snip>

>   IDE RAID is still limited to the
> 133Mb/s IDE bandwidth limit,  the more drives you add, the more you
> will hit the bandwidth limit.

I would like to comment on this one portion, everything else was 
excellent information.

The bandwidth limit of an IDE RAID controller varies GREATLY depending 
on the design. Low end 'consumer' IDE 'RAID' controllers like the 
cheaper Promise controllers are limited because a) they are software 
based, so the CPU handles all the RAID functionality and b) they tend 
to use multiple drives per IDE channel. The higher end cards like the 
3Ware (my favourite) or the Adaptec controllers are vastly different, 
they use one drive per channel (so their is no contention) and use 
dedicated processors for the parity calculations instead of the CPU. If 
you set up a RAID 0 array (not that that is _really_ raid) you would be 
able to get much much more than 133Mb/s out of a _real_ raid 
controller.

I have about 8TB of data on 3Ware 750x series IDE controllers and they 
perform very well. I also have about 8TB of data on 3Ware 950x S-ATA 
controllers and they also perform well. I am looking forward to 
building a new server with the 9550SX series S-ATA II controller.

<snip>

shawn