Re: easy project? IBM Microdrive

[mjmahon@aol.com (Michael J. Mahon)]

Dave Althoff Jr wrote:

>Michael J. Mahon (mjmahon@aol.com) wrote:
>: This brings this tread full circle!
>
>: The discussion started with a concern about the long-term write
>: endurance of CF cards used as primary "hard disks".
>
>: Even with wear levelling, and with the 100,000-class re-write
>: endurance of newer CF cards, there remains some concern about
>: the practical lifetime of these devices when used daily in a high-
>: update environment, like software development.

Thought I should update my thinking in the wake of reading the
SanDisk CF specifications..

They no longer use traditional wear-levelling, since the endurance
of a typical (16KB) block is 300,000 re-writes or better.  Instead,
the use a complex error correction code, and, when they observe
that a block is becoming error-prone (due to wear or what-have-you),
they relocate it to a spare, young block.

Since it is extremely unlikely that there would be more than a
very few blocks that get concentrated re-writes (like the bit map
in ProDOS or the FAT in a FAT file system), this approach to
managing wear-out seems quite good.

Of course, real-world experience is always the best...

>So here's a real-world question, then...
>
>On Sunday night, my 250Mb SCSI drive in my IIgs stalled.  This is a drive
>that has been up and running more-or-less 24/7 for the past ten years or
>so.  I was running a specialized text file editor in Applesoft and all the
>sudden it just quit.
>
>So...
>
>To put this system back together again, given that I have a High Speed
>SCSI card and a Vulcan power supply/case and all the cables necessary for
>an internal SCSI drive...
>
>Anybody got any sugestions for my best way to proceed?  Should I be
>digging up another tiny little SCSI drive, or should I be looking at some
>kind of SCSI->memory card adapter?

I'm not aware of any SCSI-->CF adapters--this world seems to be primarily
IDE, since CF natively supports an IDE mode.

One advantage to SCSI is the ease of connecting two drives, so that
one can easily back up the other with a speedy volume copy.
(IDE can theoretically support this, but most IDE controllers seem
to handle only a "master" drive.)

-michael

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