[plug] SCSI cards

[Bernd Felsche]

On Saturday 31 July 2004 18:28, Garry wrote:
> SCSI cards have been discussed before, but today I was asked about a
> SCSI card for speed... The guy wants to edit video under Linux. So I
> guess he'll want to gain speed and capacity using multiple PATA drives.

> I _think_ someone suggested Adaptec as a good one for Linux some time
> ago, does anyone have any current suggestions of suitable gear?

Any controllers that support U320 will provide more than enough
bandwidth. Best to use a mainboard with a couple of embedded
channels. Most of the U320 controllers require 64-bit PCI anyway -
which usually have the U320 option at reasonable cost.

PATA/SATA drives simply aren't up to speed; quite literally when
compared to the fastest SCSI. Some of the SCSI drives have sustained
throughputs in excess of 80 megabytes per second; so four on each
U320 channel are enough to saturate the channel completely.

To give you an idea of how much that is in terms of video; it's about
8 broadcast-quality video channels per SCSI drive.

A single PATA running at 7200 rpm is _enough_ for broadcast-quality
editing; but you have to be patient. If you stripe and mirror across
4 drives, then there's ample bandwidth.

The SCSI-based system has vastly greater headroom. Depending on how
well the kernel (driver) manages the IO, the CPU's FSB could be
saturated with data from 6 drives.

A 5-drive @7200 rpm PATA-based system with single 32-bit CPU and
gigabyte of RAM could be thrown together for about $2000.

A 6-drive @15,000 rpm U320 SCSI with dual Opteron (64-bit) CPUs and
a gigabyte of ECC RAM for about $5000.

You gets what you pays for.

-- 
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