[NTLUG:Discuss] Re: Fastest Access for moving large (video) files?

[Bryan J. Smith]

Chris Cox <cjcox at acm.org> wrote:
> But with striping, it's possible the 32-bit 33Mhz PCI could
> be a problem... how many drives can you handle? (could be
> greatly limited if internal to your existing machine).

Yep, this is the PITA.  There are hardly any PCIe storage
controllers out there other than the PCIe x8 LSI Logic
MegaRAID 320-2E (400MHz XScale, 128MB DRAM, 2-channel U320).

But most of the newer chipsets like the nForce4/2200/2050 do
use an internal PCIe x1 channel for their four (4) SATA
channels.  So that is at least a start (using LVM/LVM2).  No
NCQ or anything, but it's a start.

> SATA is starting to support some SCSI like features...
> that's also a plus for SATA.

I agree, NCQ is a very nice move.  Now if the OS support
would just get there.  @-p

Typically in a[n intelligent] RAID card, you don't need NCQ. 
The ASIC/microcontroller is doing command queuing for the
entire array of disks, and not just the individual disk. 
This was always the advantage of [parallel] SCSI, that the
host adapter could command and queue for an entire channel of
disks.

Serial Attached SCSI (SAS) is the next move, and should
render the death of [parallel] SCSI.

In an age when running 4 wires to a custom microcontroller
with ASIC switching, serial is here.  Now you can command 4-8
channels of direct, point-to-point storage with a card-hosted
intelligence, now that's real power.  The few SATA
controllers to date that use real SATA lines (and not just
ATA to SATA PHY conversion) are powerful solutions.

SAS increases cabling to 8m (from SATA's 1m), allows trunking
of 2, 4 and even 8 lines (0.6, 1.2 and 2.4GBps effective),
and gives hosts cards and targets, as well as host system
software, the full SCSI-2 command set.  But SAS hosts are
comaptible with SATA drives too.

SAS isn't going to be as expensive as people think.  Once the
cards come out with the Broadcom BCM8603 IC (only $60 in
quantity), you're going to have a wealth of PCI-X and PCIe
(the IC does both) controllers that do both SAS and SATA for
only several hundred bucks.

Especially for solving the darth of PCIe storage controllers
right now.


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