Re: filmscanners: Best solution for HD and images

["Moreno Polloni" <mp@dccnet.com>]

>> No one uses narrow SCSI for RAID, and it doesn't have to be SSA.  SCSI
uses
>> four bits for SCSI ID, which makes SIXTEEN devices.

>The U-160 card I know (Adaptec 29160) allows the connection of 7 devices
each controller while permitting 16 addresses.

The 7 device limit applies if you connect narrow SCSI devices. If you are
using Ultra Wide devices or drives, then you can use up to the full 15
device limit.  The 29160 has only one controller (that's why it's called
"single channel").


> I am meaning ... each disk runs at 35 or 30MB/s + SCSI architecture allows
parallel operations then I can add them to have an > aggregated transfer
rate . It might be I will never achieve 100% real addition , but I believe
the aggregated transfer rate is> close to the summary of the single
aggregated transfer rates of each disk.

If you add a second, striped drive (Raid 0), you can usually expect disk
throughput to double. If you add a third drive, the performance will be less
than triple. The biggest increase in performance is from one to two drives,
then the additive performance benefits of each additional drive is
proportionately less. A six drive Raid 0 setup, for instance, will be fast,
but nowhere near the sum of the transfer rates of each individual disk.


> > 64 bit PCI is 264M bytes/sec for 33MHz PCI,
> > and 528M bytes/sec for 66MHz PCI...so there is NO way you are saturating
the
> > PCI bus especially with a 64 bit controller.  You previously said you
were
> > on a 32 bit PCI bus.

> No, no ! As far as I know the Intel PC has a 32bit PCI but Adaptec has
implemented a 64bit adpater over a 32bit bus
>  ... they are doubling the cycle and thus keeping the compatibility with
old-standard PCI-Intel systems while improving
> the speed and throughput of the adapter (compared with 32bit adapters).

Intel-based PC's can have either 32 bit or 64 bit PCI busses, it just
depends on the motherboard. Many server and workstation motherboards have
one or more 64 bit PCI slots; most desktops have 32 bit PCI slots only. The
Adaptec 29160 can run at either 32 or 64 bits. If you install the 29160 into
a 32 bit PCI slot, it will still run fine, but it will be running at the
slower 32 bits, not 64 bits.