Re: filmscanners: Best solution for HD and images

["Ezio c/o TIN" <ezio.lucenti1@tin.it>]

> > Thus in the case of SCSI where you cannot (by definition) overcome the
> > number of 6 devices x chain/controller,
>
> WHAT SCSI are you talking about?  Try 16. not 6.
>

How many addresses have you per controller ?
from 0 to 6 = 7 but 1 is the controller itself.
SCSI is not IBM SSA . SCSI = 6 devices x controller/chain ; SSA 16 devices x
controller/loop

> That's not true.  There is no "double write", both the data/parity is
> written at the same time.  Parity can easily be calculated on the fly.
>

YEP !  and who does write it on the disk in a different area/zone/disk ?

> Run some benchmarks on your system and see for your self.  Also, make sure
> the benchmarks AREN'T running out of disk cache...that hardly tests the
disk
> speed.  You'll be lucky to get even near 80, if even 60.

My data are the output of a benchmark and not the theoretical max speed.
Yes you can add because SCSI can parallelize the requests while IDE cannot.

> The standard PCI bus is 33 MHz (or 66MHz), NOT 133MHz.  Perhaps you mean
> 132M BYTES/sec?  Even at that, you can't get near %80 of that, if you're
> lucky.  132M bytes/sec is the burst rate.  There is substantial overhead
on
> the PCI bus that lowers that substantially.
>

YEP ! I can achieve the saturation of bus before achieving the saturation of
the controller (Adaptec 29160 is a 64 bit adapter).

Sincerely.

Ezio

www.lucenti.com  e-photography site


----- Original Message -----
From: "Austin Franklin" <darkroom@ix.netcom.com>
To: <filmscanners@halftone.co.uk>
Sent: Monday, November 12, 2001 4:21 AM
Subject: RE: filmscanners: Best solution for HD and images


> > Thus in the case of SCSI where you cannot (by definition) overcome the
> > number of 6 devices x chain/controller,
>
> WHAT SCSI are you talking about?  Try 16. not 6.
>
> > BTW , this method compulsorily implies a DOUBLE WRITING need i.e.
> > write the
> > data + write the new parity (even if on another disk) and this is
> > meaning a
> > LOSS OF SPEED/EFFICIENCY (relatively to the achievable speed/efficiency
of
> > the disks)
>
> That's not true.  There is no "double write", both the data/parity is
> written at the same time.  Parity can easily be calculated on the fly.
>
> > Yesterday night I have bought on eBay an IBM U-160 10000rpm 18GB new and
> > under warranty for 102 USD + 20$ of shipment to Italy from USA
> > and this unit
> > will be the fourth inside my system while having 2 x CD/R (IDE)
> > and 1 x DVD
> > (IDE) .
> > My aggregated sustained transfer rate is 3 x 35MB/s + 1 x 29MB/s
> > = 134MB/s =
>
> The data rate doesn't just "aggregate" like that.  There is SCSI overhead
> that decreases the effective overall transfer rate.  Not all files are
> sequential, and without spindle locking, there is quite a bit of latency.
> Run some benchmarks on your system and see for your self.  Also, make sure
> the benchmarks AREN'T running out of disk cache...that hardly tests the
disk
> speed.  You'll be lucky to get even near 80, if even 60.
>
> > the limit of a 32bit PCI bus at 133MHz (but still in the limits of an
> > Adaptec 29160 controller)
>
> The standard PCI bus is 33 MHz (or 66MHz), NOT 133MHz.  Perhaps you mean
> 132M BYTES/sec?  Even at that, you can't get near %80 of that, if you're
> lucky.  132M bytes/sec is the burst rate.  There is substantial overhead
on
> the PCI bus that lowers that substantially.
>
>