[Novalug] best hard disk setup for home file server?

[Bryan J Smith]

Density defines performance heavily in disk.  Getting the bits off
is not the problem, it's the mechanical aspects.

And once again, you're another personal that confuses RAM and
EEPROM.  DRAM slaughters EEPROM technologies, orders of
magnitude.  NAND EEPROM is not accessed like DRAM, but
people assume otherwise.

It's the difference between tens of nanoseconds and microseconds - huge.

Oversimplified:  
- DRAM is nanoseconds (typically 20ns or so)
- NAND EEPROM is microseconds (varies wildly)
- Disk is milliseconds

DRAM block switching is also much faster than NAND EEPROM,
and the latter is much faster than disk seek.  Do not make the
mistake of saying RAM and EEPROM in the same statement as
they are _nothing_ like each other at all, period.

--  
Bryan J Smith - mailto:b.j.smith at ieee.org  
http://www.linkedin.com/in/bjsmith
Sent via BlackBerry from T-Mobile  
    

-----Original Message-----
From: James Ewing Cottrell 3rd <JECottrell3 at comcast.net>
Date: Fri, 16 Oct 2009 14:07:36 
To: <b.j.smith at ieee.org>
Cc: Nino Pereira<pereira at speakeasy.net>; Novalug<novalug at calypso2.tux.org>
Subject: Re: [Novalug] best hard disk setup for home file server?

pardon me, i wasn't clear. i was comparing the time to read the actual 
bits off the magnetic media with the rotational and seek delays. and 
even if you had a disk with only one track that rotated infinitely fast, 
that would still be your limiting factor.

i expect things will get much better with both ram and eeprom. ten years 
ago i bought my first pc, and it had 13G disks for which i paid about 
$100. now i can buy a 16G flash drive for $40 or even less.

which would you want to run a small computer on as the only disk? i 
think the answer is still the real disk, but what will it be in 5 years?

heck, by then we might have some other form of flash drive than eeprom 
and will almost certainly have some access method better than usb 2.0.

jim

Bryan J Smith wrote:
> Actually, that's not true.  NAND EEPROM has it's latency issues.
> The disk rotation/seek is far more costly.  Hard drives, when written
> to sequentially, actually rival NAND EEPROM, depending on design.
> 
> NAND EEPROM has its overhead in random access, magnitudes
> worse than DRAM (let alone SRAM), but disk rotation/seek is
> magnitudes worse than it.  EEPROM technologies are not RAM,
> despite assumptions.  In fact, magnetic can best it in various ways.
> 
> ------Original Message------
> From: James Ewing Cottrell 3rd
> To: Bryan J. Smith
> Cc: Nino Pereira
> Cc: Novalug
> Sent: Oct 16, 2009 12:49
> Subject: Re: [Novalug] best hard disk setup for home file server?
> 
> Bryan J. Smith wrote:
>> NAND EEPROM compared to magnetic disk, yes.
>> NAND EEPROM compared to DRAM, hell no (let alone SRAM).  ;)
>> NAND EEPROM has its latency issues as well, just far less than disk.
> 
> i did indeed leave that complication out. it also takes time to rip the 
> bits off the magnetic media or out of the flip flops in memory, but in 
> the case of magnetic media that time pales in comparison to the 
> rotational and seek latency.
> 
> jim
> 
> 
> --  
> Bryan J Smith - mailto:b.j.smith at ieee.org  
> http://www.linkedin.com/in/bjsmith
> Sent via BlackBerry from T-Mobile  
>     
> 
> 
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