> > 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" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> 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. > >