[WinMac] Re: USB-Serial

Daniel L. Schwartz(expresso[at]snip.net)
Thu, 25 Mar 1999 23:25:12 -0500

        Dear John,

        No, there IS some rudimentary UPS monitoring software for the Mac (<=MacOS
8.5.1).

        The problem arises in that this software is only set up to monitor a Mac
(RS-422) printer or modem port -- Not a Mac USB port.

        What this means is that if you have either an iMac or a blue & white G3
Mac -- Both of which have had the RS-422 serial ports "Steveified" -- You
can't interface a UPS to either of these machines.

        Yes, you can hook up a standard UPS to these machines... But a *critical*
component is the signalling of the UPS' status back to the computer it's
supplying power to. For a couple of minutes, this is not important... But
after about 2 minutes, you want to send the status of the UPS back to the
computer, so that when the batteries start to die down, the computer can
initiate a graceful shutdown.

        Even though both NetWare and NT have a built-in UPS service, the operating
systems have, built in, transactional file systems. This means if you "pull
the plug" all disk writes have been journalled... Either the committed disk
writes have actually occurred; or they WILL occur on the next power-up. You
have a level of redundancy here: Both a graceful shutdown mechanism as well
as a transactional file system.

        Now, let's contrast this to the MacOS' HFS and HFS+ (Hierarchical File
System and Hierarchical File System (Extended)): These file systems,
although decent, lack redundancy in that uncommitted writes can be lost in
the event of an ungraceful shutdown.

        This is flawed on two distinct counts:

        1) For the iMac and blue & white G3, there is NO WAY for an
Uninterruptible Power Supply to signal the Mac that its batteries are
almost dead;

        2) More importantly, when a Mac crashes and HFS or HFS Extended starts to
become corrupted, this makes the Finder more prone to crashing. And the
more often the Finder crashes, the more prone the f8ile system will become
corrupted...

        Putting the Mac in a "Catch-22" and putting it into a downward spiral.

        And you want to use this for an enterprise - Or even production - server?

        Yours truly,
        Dan Schwartz

At 10:21 PM 3/25/99 -0500, you wrote:
>Dan,
>
>I get the feeling that this is something of a moving target, but maybe you
>can straighten me out:
>
>You wrote:
>> Yes, there are USB <--> serial converters. Unfortunately, they still fall
>> into the same pitfall that the APC BackUPS Pro twins fall into... No
>driver
>> software.
>
>I take this to mean no Mac software for the APC backup unit. Do you mean to
>say then that there's no decent Mac backup system at all, regardless of
>port variety (which would be a different problem from no USB units, which
>seem to have the problem you originally mentioned:
>
>> The problem is with both the iMac and the blue & white G3's: There's no
>> graceful shutdown available from the UPS, because there's no serial
>> input.
>
>)?
>
>John D. Muccigrosso
>

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