Reply to Gene's Comments on High Availability Environments

Mon Jan 6 03:44:45 PST 1997

* From the SCSI Reflector (scsi at symbios.com), posted by:
* "Paul D. Aloisi 603-429-8687 aloisi at unitrode.com" <ALOISI at uicc.com>
*
Gene,

4 Small systems often use SCSI for interconnects outside of the box. I have
used SCSI on every system even before I worked on the SCSI committee. It
works for transporting media form system to system. Before the JAZ drives
I use to transprot work between systems on SCSI drives, files were often
too large for floppies and tapes take too long. Scanners are still often
only available with a SCSI interface. 

ATA is fine for one or two disks on a system, when you only use that
system in a closed environment, but for most people that use PC as
a work place for where they are at, it is too restrictive. Currently
I use an Iomega JAZ drive and cartridges to carry my work to where I
am, before I use to use drives.

33. Terminators are an issue when hot plugging if you are not using the SCA-2 
connector. Termpower is bypassed on every drive, when the drive is hot
plugged the termpower line is glitched. Passive terminators pass the glitch
directly to the pull up level. Active terminators have regulators with
bypassing that will ride through hot plugging without effecting the
pullup level.

67. SCA-2 connector on a drive does not have a terminator, but several
companies use standard drives with an adapter card that connects to
SCA-2. There are terminators on the drive which are powered from the drive
since there is no termpower on the SCA-2 connector.

Note: on all the systems that I currently use at home, work and on the
road, I use a combination of ATA and SCSI drives. ATA is fine for a low
cost drive that I upgrade year or so. It is good for the operating system
and applications, but my user files and larger storage I use SCSI drives.

Paul Aloisi
Unitrode
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