[Info-vax] HP wins Oracle Itanium case

[Paul Sture]

On Thu, 23 Aug 2012 03:15:30 +0200, Johnny Billquist wrote:

> On 2012-08-23 00:09, ChrisQ wrote:
>> On 08/22/12 19:52, Johnny Billquist wrote:
>>
>>
>>> Uh... No. At the lowest level of a disk, you do *not* store a stream
>>> of bytes. Where on earth did you get that from? At the lowest level, a
>>> disk deals with disk *blocks*. You read/write one block at a time.
>>> Blocks are typically 512 bytes, or possibly 2048 or 4096 bytes
>>> nowadays.
>>
>> Err, thanks, but I am aware of all that. It is a stream of bytes, it
>> just happens to be formatted into blocks on the disk, for
>> identification, error checking and recovery.
> 
> It's a disk block. You might then have implemented some abstraction
> layer on top of that, along with some metadata, to make it look like
> your disk provides you with a stream of bytes. But that is actually not
> the physical truth, but a lie presented to you with the help of a lot of
> software. And sometimes the truth shines through.

Yes.  Going back to my ICL days, it was standard practice to minimise 
head movement by manually placing files on disk by cylinder or group of 
cylinders, i.e. the same disk track on multiple platters of a physical 
drive.
 
>> If you read back in the thread, you'll see that what i'm really getting
>> at is that a byte  stream is the most generic / lowest common
>> denominator, from which all other data formats can be layered on top
>> of.
> 
> Except you will get a block, and not a stream of bytes, when you read
> from a disk. If your "stream of bytes" supposedly were just 10 bytes,
> you would still get one block of bytes from the disk. The other 502
> bytes will also be something. You will then have to write a layer on top
> of the block nature of a disk to try and hide this truth.

When we get to RMS, the program may be presented with a "stream of 
bytes", but the underlying data isn't that.  For example sequential 
records can be word or longword aligned, even though you don't see this 
unless you look at the file in block mode.

Besides all that, a product I used many years ago abused the word 
"stream".  What it really meant in that product was "file handle", but 
the marketing types had obviously got in on the act and injected the word 
"stream".  They even layered some so-called security on top of that but 
it was really smoke and mirrors.

-- 
Paul Sture