10 Apr
2013
10 Apr
'13
4:42 p.m.
Arno Kletzander wrote:
OK, seems we mixed up logically and physically large
drives here.
I have about none of the first, but several of the latter category amongst those in
question for the machines we're discussing here:
1(2)x RD53 5,25" MFM
Please be aware that most (maybe now almost all) RD53
drives have failed with the head stuck problem. If you have
an RD53 which can still be read, it is strongly suggested that
you copy the contents to a more reliable drive. It is possible
to open and remove the sticky mess without a clean room,
but read the notes over the past 5 or 10 years which describe
how it should be done. I would agree to use an RD53 as a
scratch drive for temporary storage, but not for saving files
after the drive is powered down. If anyone has any MTBF
stats after the sticky mess has been removed in terms of
how many hours of actually using the drive, that would be
helpful.
1x 300MB 5,25" ESDI,
I have a number of Micropolis ESDI and Hitachi ESDI
drives which seem to be quite reliable. Most are the
Hitachi DK-515 ESDI 5 1/4" 600 MB drives. They
are used with a PDP-11/83 system with their own
PC type power supply and fan since I doubt that using
the internal power supply from the BA123 is helpful.
Those Hitachi drives arrived 4 in a box with that PC
type power supply in the first place which emulated
one of the VAX type of drives which DEC supported.
Since the ESDI drives were exactly what I wanted for
the PDP-11/83 and the DEC reseller had no demand
for these drives from VAX users, the price and usage
was perfect for the PDP-11/83 with an MSCP EDSI
controller. Normally, I used 3 * 600 MB drives which
were usually all identical with drive 0 being the production
drive and drives 1 and 2 being backups.
3x 5MB 14" RL01,
1x 10MB 14" RL02,
VERY reasonable for a small RT-11 system, but prone
to hardware problems (especially filters) in the long run.
(2x 80MB 14" SMD) (I just have a lead on those
yet)
The ESDI drives are more reliable and faster. ESDI controllers
were also less expensive and more available.
[TK50 tape subsystem]
From my point of view, one of the worst backups that
DEC ever produced. While making a simple copy of
a large file is reasonable, the lack of a reasonable
streaming capability makes use of small files or a verify
of a large file extremely difficult. On the other hand,
the TK70 is a good, fast, reliable drive which I used
for many years as my primary backup until I found
some Sony SMO S-501 magneto optical drives.
Jerome Fine