neese@adaptx1.UUCP (06/01/91)
>>I currently have a 386sx with a Seagate ST-02 and ST296N SCSI disk. >>With CORETEST and with Nortons SI benchmark, I get a reading of about >>220-300 K bytes/sec transfer time, and a 28-31 ms access time. >> >>I currently operate DOS and sometimes Windows 3.0 now. Sometime >>in the future (6-12 months), I'd like to be able to use OS/2 2.0 or >>Unix. >> >>1) What performance increase can I expect with a adapter card >> like the IN2000 or ADAPTEC 1542B, using the same ST296N disk. > >Under Windows 3.0, you will notice a (perhaps significant) decrease in >transfer rate if you go to a bus-mastering controller due to the double >buffering used to work around the physical-to-virtual translation. Nope. Under Windows 3.0, if the bus master driver understands the INT4B (VDS) services, the driver can request a physical memory location from the logical address. Not a bad performance hit at all. Prior to the VDS services, one had to do double buffering and hope no other program relocated the driver and buffer. >STUFF DELETED >>5) In planning to goto OS/2 2.0 or Unix in the future, what should >> I avoid purchasing? > >Avoid non-bus-mastering host adapters. Overhead under a multi-threaded OS >is very high for these critters (Always is not bus-mastering, Adaptec 154x >and WD7000 are). Agree. >>Should I change my idea of getting a SCSI >> adapter alltogether, and just get a faster IDE or ESDI drive, and >> keep the old card? > >SCSI is easier to integrate and (with some drivers) more reliable. ESDI is >faster in a single disk or single threaded system, SCSI is faster in a >mult-disk and multi-threaded system. If you're going with Unix, you can add >tape and CD-rom to the same host adapter that drives your disk. > >With most SCSI disks, if you develop a defect in an awkward place, you can >reformat to "remove" it; formatting maps out defective blocks, presenting a >flawless image of the media. Some drivers, like the ones we sell with our >products :-), are smart enough to remap defects on-the-fly, so you'll never >even see one until you run out of spares. Reformat and you can gain a new >set of spares. With ESDI, you're SOL. Or you can have the drive do the actual remapping. Some of the higher end drives support thia, but have it turned off. One can also setup the error page to have the drive recover all the data it can before remapping the suspect sector. Roy Neese Adaptec Senior SCSI Applications Engineer UUCP @ neese@adaptex uunet!cs.utexas.edu!utacfd!merch!adaptex!neese
iverson@xstor.com (Tim Iverson) (06/04/91)
In article <283400133@adaptx1> neese@adaptx1.UUCP writes: >>Under Windows 3.0, you will notice a (perhaps significant) decrease in >>transfer rate if you go to a bus-mastering controller due to the double >>buffering used to work around the physical-to-virtual translation. > >Nope. [...] >Prior to the VDS services, one had to do double buffering and hope no >other program relocated the driver and buffer. I was aware of this, but I didn't know that the Adaptec driver actually used this method - which, of course, is obviously far preferable to the double-buffering hack required before virtual-to-physical translation was available. >>flawless image of the media. Some drivers, like the ones we sell with our >>products :-), are smart enough to remap defects on-the-fly, so you'll never >>even see one until you run out of spares. Reformat and you can gain a new >Or you can have the drive do the actual remapping. Some of the higher end >drives support this, but have it turned off. One can also setup the error >page to have the drive recover all the data it can before remapping the >suspect sector. This is true, but all is not roses. Consult your OEM manual very carefully before relying on this method. An example: the Wren VI HH says it supports AWRE (automatic write reassign enable), but if you read closely, you'll see that it only reassigns if the header is corrupt - this means that the data could be bad (and the drive might know this if you do a write with verify), but it won't reassign. Erasable optical drives have similar problems. Of course, if you're using a driver that does not support recovery, then AWRE (or even ARRE) is your only recourse. > Roy Neese > Adaptec Senior SCSI Applications Engineer > UUCP @ neese@adaptex > uunet!cs.utexas.edu!utacfd!merch!adaptex!neese - Tim Iverson iverson@xstor.com -/- uunet!xstor!iverson