I couldn't find this information on Google, but why is the
visual representation of a database (in presentations and
graphical descriptions) always a can or a cylinder? Is it
because hard drives contain cylinders or is it because that
is what hard drives used to look like before the rectangular
ones appeared?

Thanks,
Josh

I couldn't find this information on Google, but why is the
visual representation of a database (in presentations and
graphical descriptions) always a can or a cylinder? Is it
because hard drives contain cylinders or is it because that
is what hard drives used to look like before the rectangular
ones appeared?

howfie <yadayada at (no spam) yabloo.com> wrote:

I couldn't find this information on Google, but why is the
visual representation of a database (in presentations and
graphical descriptions) always a can or a cylinder? Is it
because hard drives contain cylinders or is it because that
is what hard drives used to look like before the rectangular
ones appeared?

Correct. See http://en.wikipedia.org/wiki/Early_IBM_disk_storage#IBM_3330
for a
picture of such. And that is basically what you would see inside a
modern hard
drive. Mind you that one is 200 Mb. I've seen others in 1979 which were
mounted in
a machine slightly narrower than a washing machien and were 10 Mb.

"Tony Toews [MVP]" <ttoews at (no spam) telusplanet.net> wrote in message
news:t86b35lf6hqj2niterb2hirsni7cm300vr at (no spam) 4ax.com...
howfie <yadayada at (no spam) yabloo.com> wrote:

I couldn't find this information on Google, but why is the
visual representation of a database (in presentations and
graphical descriptions) always a can or a cylinder? Is it
because hard drives contain cylinders or is it because that
is what hard drives used to look like before the rectangular
ones appeared?

Correct. See
http://en.wikipedia.org/wiki/Early_IBM_disk_storage#IBM_3330 for a
picture of such. And that is basically what you would see inside a
modern hard
drive. Mind you that one is 200 Mb. I've seen others in 1979 which
were mounted in
a machine slightly narrower than a washing machien and were 10 Mb.

Also see the wikipedia article on drum memory.
Cool, thanks for all the info guys. I just wanted to be 100%

http://en.wikipedia.org/wiki/Magnetic_drum

The picture of the drum in the article really looks like a can. Drums
fell out of favor when compared to discs, because moveable heads made
for much cheaper construction.
In addition, stacking disk on top of each other in cylinder fashion
allowed you to pack more media onto the same square footage of floor
space. The great timesharing computers of the 1964-1982 time frame
all used discs of various sizes and capacities, as did the giant
database mainframes of the era. The early computers in the 1950s
tended to use drums for main memory, before core memory gained
widespread use. See the article on the IBM 650.
http://en.wikipedia.org/wiki/IBM_650

"Walter Mitty" <wamitty at (no spam) verizon.net> wrote in
news:wDpZl.1097$P5.777 at (no spam) nwrddc02.gnilink.net:

"Tony Toews [MVP]" <ttoews at (no spam) telusplanet.net> wrote in message
news:t86b35lf6hqj2niterb2hirsni7cm300vr at (no spam) 4ax.com...
howfie <yadayada at (no spam) yabloo.com> wrote:

I couldn't find this information on Google, but why is the
visual representation of a database (in presentations and
graphical descriptions) always a can or a cylinder? Is it
because hard drives contain cylinders or is it because that
is what hard drives used to look like before the rectangular
ones appeared?
Correct. See
http://en.wikipedia.org/wiki/Early_IBM_disk_storage#IBM_3330 for a
picture of such. And that is basically what you would see inside a
modern hard
drive. Mind you that one is 200 Mb. I've seen others in 1979 which
were mounted in
a machine slightly narrower than a washing machien and were 10 Mb.
Also see the wikipedia article on drum memory.
Cool, thanks for all the info guys. I just wanted to be 100%
sure before I said anything to my database students or add
it to my powerpoints .

Josh

http://en.wikipedia.org/wiki/Magnetic_drum

The picture of the drum in the article really looks like a can. Drums
fell out of favor when compared to discs, because moveable heads made
for much cheaper construction.
In addition, stacking disk on top of each other in cylinder fashion
allowed you to pack more media onto the same square footage of floor
space. The great timesharing computers of the 1964-1982 time frame
all used discs of various sizes and capacities, as did the giant
database mainframes of the era. The early computers in the 1950s
tended to use drums for main memory, before core memory gained
widespread use. See the article on the IBM 650.
http://en.wikipedia.org/wiki/IBM_650

howfie wrote:
"Walter Mitty" <wamitty at (no spam) verizon.net> wrote in
news:wDpZl.1097$P5.777 at (no spam) nwrddc02.gnilink.net:
"Tony Toews [MVP]" <ttoews at (no spam) telusplanet.net> wrote in message
news:t86b35lf6hqj2niterb2hirsni7cm300vr at (no spam) 4ax.com...
howfie <yadayada at (no spam) yabloo.com> wrote:

I couldn't find this information on Google, but why is the
visual representation of a database (in presentations and
graphical descriptions) always a can or a cylinder? Is it
because hard drives contain cylinders or is it because that
is what hard drives used to look like before the rectangular
ones appeared?
Correct. See
http://en.wikipedia.org/wiki/Early_IBM_disk_storage#IBM_3330 for a
picture of such. And that is basically what you would see inside a
modern hard
drive. Mind you that one is 200 Mb. I've seen others in 1979 which
were mounted in
a machine slightly narrower than a washing machien and were 10 Mb.
Also see the wikipedia article on drum memory.
Cool, thanks for all the info guys. I just wanted to be 100%
sure before I said anything to my database students or add
it to my powerpoints .

Josh

http://en.wikipedia.org/wiki/Magnetic_drum

The picture of the drum in the article really looks like a can. Drums
fell out of favor when compared to discs, because moveable heads made
for much cheaper construction.
In addition, stacking disk on top of each other in cylinder fashion
allowed you to pack more media onto the same square footage of floor
space. The great timesharing computers of the 1964-1982 time frame
all used discs of various sizes and capacities, as did the giant
database mainframes of the era. The early computers in the 1950s
tended to use drums for main memory, before core memory gained
widespread use. See the article on the IBM 650.
http://en.wikipedia.org/wiki/IBM_650


I must say I thought it was one of the greatest questions I've ever seen
here. And half-thought it was a send-up until Walter replied! If this is
for real, maybe you should point out to the kids that the cylinders were
and are 'virtual', get them used to what that term can mean.

pace? I have to
wonder how things would be now if today's main memory were available then,
a lot of decisions would have been different. Of course we know what
really happened to that memory - as a friend who was an IBM salesman in
the 1960's was told when some 512KB memory cpu's came out: "your customers
can't use it, we need most of it for OS/360'. In those days the famous
IBM motto was "THINK" and they used to give out desk plaques to remind you
to do that. I saw one that had been graffitee'd to say "THINK OR THWIM".
.

Then there's memory capacity. Did you know that even into the 1990's a
typical PARS/ACP flight reservation system for a medium-sized airline
(say 100-300 planes) occupied only about 300MB disk space? I have to
wonder how things would be now if today's main memory were available
then, a lot of decisions would have been different. Of course we know
what really happened to that memory - as a friend who was an IBM
salesman in the 1960's was told when some 512KB memory cpu's came out:
"your customers can't use it, we need most of it for OS/360'. In those
days the famous IBM motto was "THINK" and they used to give out desk
plaques to remind you to do that. I saw one that had been graffitee'd
to say "THINK OR THWIM".

I must say I thought it was one of the greatest questions I've ever
seen
here. And half-thought it was a send-up until Walter replied! If this
is for real, maybe you should point out to the kids that the cylinders
were and are 'virtual', get them used to what that term can mean.


Once, I was given a 2321 (if I recall the model), sometimes called a
spaghetti picker. Real Buck Rogers concept, half disk and half tape
(with an astounding 500 msec access/latency time) but with serious
engineering, like a three-horsepower motor labelled "lubricate every
twenty years", no guff. Serious Nasa-style hydraulics, twenty gallon
reservoir and compressed nitrogen. I couldn't afford to hook it up. I
knew a really smart programmer but much younger who asked me what a
mainframe disk looked like. I told him the box that held seven or
eight
of them was taller and longer than him so the 'Customer Engineer' (who
was a regular presence at all big IBM installations right up to about
twenty years ago) could get his head inside. Unfortunately it seems
one
CE was decapitated which resulted in an EC, so-called "engineering
change".


When I thought again about his question afterwards I remembered how
much
closer programming was to manual labour I was envious of that kid
because he had saved himself a lot of wasted years and I wished I had
been born later. On some smaller machines even in the 1960's, people
used tape drives for working storage to sort. These days, for myself,
I
just use solid state stuff.


In those days a macho term among assembler programmers was
'bare-metal-programming', which the typical disks encouraged with the
'Count-Key-Data' instructions that were wired into their controllers.
Thankfully, modern disks have abstracted out that physical nonsense.
The same people considered it important to flip three thousand cards
without spilling them and looked down their noses at any object deck
that was thinner than three or four inches.


Then there's memory capacity. Did you know that even into the 1990's a
typical PARS/ACP flight reservation system for a medium-sized airline
(say 100-300 planes) occupied only about 300MB disk space? I have to
wonder how things would be now if today's main memory were available
then, a lot of decisions would have been different. Of course we know
what really happened to that memory - as a friend who was an IBM
salesman in the 1960's was told when some 512KB memory cpu's came out:
"your customers can't use it, we need most of it for OS/360'. In those
days the famous IBM motto was "THINK" and they used to give out desk
plaques to remind you to do that. I saw one that had been graffitee'd
to say "THINK OR THWIM".
.

Hi Paul,

Thanks for the info. With pictures like this,
http://www.columbia.edu/acis/history/cell2.jpg,
I guess it's easy to see why it's always a can or a cylinder.

Could you discuss a little more about your 'cylinders are virtual'
comment? ...

Walter Mitty wrote:
"howfie" <yadayada at (no spam) yabloo.com> wrote in message
news:Xns9C31ABF92C6E6yadayadayabloocom at (no spam) 216.196.97.131...
Hi Paul,

Thanks for the info. With pictures like this,
http://www.columbia.edu/acis/history/cell2.jpg,
I guess it's easy to see why it's always a can or a cylinder.
...

Hi Paul,

Thanks for the info. With pictures like this,
http://www.columbia.edu/acis/history/cell2.jpg,
I guess it's easy to see why it's always a can or a cylinder.
...

Looks to me that it's only a matter of time before Solid State Disks
take over.

"howfie" <yadayada at (no spam) yabloo.com> wrote in message
news:Xns9C31ABF92C6E6yadayadayabloocom at (no spam) 216.196.97.131...
Hi Paul,

Thanks for the info. With pictures like this,
http://www.columbia.edu/acis/history/cell2.jpg,
I guess it's easy to see why it's always a can or a cylinder.

Could you discuss a little more about your 'cylinders are virtual'
comment? I'm not really a hardware guy and this question is actually for
a simple introductory relational database course that I teach which
exclusively focuses on 'the query' and SQL. In the first lecture though,
I really like to talk about the history of databases and other little
tidbits of potentially useful (or useless) information.

Thanks!

I'm not sure what "cylinders are virtual" meant. I await Paul's response.

The term "cylinders" does come up repeatedly when discussing stacked disk
platters at the physical level.

When a spindle holds a stack of disk platters, there is one head for each
surface that's actually used. These heads generally move together as a
unit, in what's called a "seek" operation.
Once a seek is done, each head can read/write one track worth of data.
If you put all these tracks together, they make up a "cylinder". This is
the total amount of data that can be read or written before another seek
has to be performed. Typically, the disk unit reads or writes a small
percentage of the cylinder before performing the next seek, but that
depnds on the usage pattern.

When disk geometry is viewed this way, a track can be seen as the
intersection of a cylinder and a surface.

The disks pretend there are x sectors on each y cylinders on each z

"Walter Mitty" <wamitty at (no spam) verizon.net> skrev i en meddelelse
news:HXK%l.580$NF6.84 at (no spam) nwrddc02.gnilink.net...

"howfie" <yadayada at (no spam) yabloo.com> wrote in message
news:Xns9C31ABF92C6E6yadayadayabloocom at (no spam) 216.196.97.131...
Hi Paul,

Thanks for the info. With pictures like this,
http://www.columbia.edu/acis/history/cell2.jpg,
I guess it's easy to see why it's always a can or a cylinder.

Could you discuss a little more about your 'cylinders are virtual'
comment? I'm not really a hardware guy and this question is actually for
a simple introductory relational database course that I teach which
exclusively focuses on 'the query' and SQL. In the first lecture though,
I really like to talk about the history of databases and other little
tidbits of potentially useful (or useless) information.

Thanks!

I'm not sure what "cylinders are virtual" meant. I await Paul's response.

The term "cylinders" does come up repeatedly when discussing stacked disk
platters at the physical level.

When a spindle holds a stack of disk platters, there is one head for each
surface that's actually used. These heads generally move together as a
unit, in what's called a "seek" operation.
Once a seek is done, each head can read/write one track worth of data.
If you put all these tracks together, they make up a "cylinder". This is
the total amount of data that can be read or written before another seek
has to be performed. Typically, the disk unit reads or writes a small
percentage of the cylinder before performing the next seek, but that
depnds on the usage pattern.

When disk geometry is viewed this way, a track can be seen as the
intersection of a cylinder and a surface.

The disks pretend there are x sectors on each y cylinders on each z
surfaces, giving a total of x*y*z sectors.

However, there are more sectors on the outer cylinders than the inner
cylinders, so the disk drive internally calculates what the logical sector
corresponds to in actual sector/cylinder/head.

That's why a disk can appear to have 64 heads. Just so large disks can be
compatible with old bios'es. I believe there is a limit on 1024 cylinders on
some bios or os'es.