Xah Lee's Unixism
firstname at lastname.pr1v.n0
Fri Sep 10 21:08:58 CEST 2004
In article <ullfinq1o.fsf at mail.comcast.net>,
Anne & Lynn Wheeler <lynn at garlic.com> wrote:
>Morten Reistad <firstname at lastname.pr1v.n0> writes:
>> smD the TLA that represents a washing-machine size disk. Mountable.
>> ^ Made impressive head crashes from time to time.
>> But I won't interfere with this lovely thread drift with lots
>> of relevant facts.
>the first disks i played with at the univ. were 2311s on 360/30; they
>were individual, top-loading, with mountable disk packs; 2311 disk
>pack was a little over 7mbytes. didn't find picture of 2311 ... but
>this picture of 1311 were similar ... the lid of the unit was released
>and raised (something like auto engine hood)
>the next were 2314s that came with 360/67. it was long single unit
>with drive drawers that slid out. top & bottom row with 9 drives.
>drives had addressing plugs .... eight plus a spare. a 2314 pack could
>be mounted on the spare drive, spun up .... and then the addressing
>plug pop'ed from an active unit and put in the spare drive. it reduced
>the elapsed time that the system saw unavailable drive (time to power
>off a drive, open the drawer, remove a pack, place in new pack, close
>drawer, power up the drive). 2314 pack was about 29 mbytes. picture
>of 2314 cabinet
>the next were the 3330s ... long cabinet unit looked similar to 2314
>... but with only 8 drawers (instead of 9). 3330-i pack had 100mbytes
>... later 3330-ii pack had 200mbytes. picutre of 3330 unit ... the three
>cloaded plastic units on top of the unit were used to remove disk pack
>and hold it.
These are the IBM gear that most resemble SMB equipment. SMD's were
the BUNCH answer to DEC's RP04/5/6 and IBM's 3330. Originally made
by CDC; others also produced them. NCR and Fujitsu come to mind.
Originally existed as 80-megabyte, pretty light units (30 kg);
later expanded to 160-megabyte. Then the real washing machines
turned up; 300 mb (315 unformatted megabytes). Originally 4 on a chain,
15 mbit analogue readout (MFM ISTR; they never tried RLL).
These were a mainstay among the smaller mini vendors from approx 1974
to the advent of winchesters around a decade later. The earliest
winchesters made exact hardware replicas of the SMD. Then the
spec was expanded and became ESMD, but ESMD was never as robustly
standardized. Sacrifices of goats, PHBs and undergraduates was needed
to stabelize long ESMD chains.
>close up of 3330 disk pack in its storage case ... also has picture
>of 3850 tape cartridges
>misc. other storage pictures:
>next big change was 3380 drives with totally enclosed, non-mountable
>old posting on various speeds and feeds
>http://www.garlic.com/~lynn/95.html#8 3330 disk drives
>and some more old performance data
>http://www.garlic.com/~lynn/95.html#10 virtual memory
>i had written a report that relative disk system performance had
>declined by a factor of ten times over a period of 10-15 years. the
>disk division assigned their performance group to refute the
>claim. they looked at it for a couple of months and concluded that i
>had somewhat understated the relative system performance decline
>... that it was actually more. the issue was that other system
>components had increased in performance by 40-50 times ... while disks
>had only increased in performance by 4-5 times ... making relative
>disk system performance 1/10th what it had been. misc. past posts
>about the gpd performance group looking at the relative system
And we are still on that line.
Nowadays most heavy production database data really stays in memory;
with the disk as a backup medium.
More information about the Python-list