[Info-vax] The Future of Server Hardware?

[Johnny Billquist]

On 2012-10-04 20:03, glen herrmannsfeldt wrote:
> Johnny Billquist <bqt at softjar.se> wrote:
>
> (snip, I wrote)
>>> For many years, 3600 RPM disks have been common, so 8.33ms average
>>> rotational delay. For servers, now, 7200RPM might be more usual,
>>> ro 4.16ms. A million instructions doesn't sound far off.
>
>> 3600 rpm? I didn't even know you could find that anymore. I thought the
>> standard for any cheap home PC was 7200 RPM.
>
> For current model Seagate, from the seagate.com web site, and
> for desktop (presumably 3.5in) drives, the choices seem to be
> 5900RPM and 7200RPM. For laptop drives, 5400 and 7200RPM.
> (Maybe the 5900 is a typo.)  Western Digital has a green
> (for eco-computing) line which doesn't indicate the RPM
> (at says intellipower) but which some sites claim as 5400.
>
> Looks to me like 5400 is usual for cheaper or more power
> efficient home PCs and 7200 for more expensive ones.

So noone seems be to able to dig up any trace of any 3600 rpm disks... 
Good. I was realy wondering if I had missed something.

>> For people who really care
>> about performance, and have money, 15.000 RPM is common, and I think you
>> can also find 18.000 RPM. However, I guess that market is now going for
>> SSD instead.
>
> I am usually a little behind the curve. I believe the fastest
> that I have seen (not just read about) is 10,000RPM.

You are just not at the right places then. :-)
Oh, and I should point out that ATA and SATA disks have never been close 
to the bleeding edge, so if that is your disk interface of choice, then 
you'll probably not find anything faster than 7200 rpm.

> Still, 18,000RPM is five times faster than the big 14 inch
> drives of 40 years ago, and 5400 only 1.5 times faster.

Right. Disks are so mechanical that it's hard to do Moore's law in some 
aspects.

>> But since CPUs are screaming fast, I'm pretty sure 1 million
>> instructions are probably still true.
>> Also, don't forget that rotational latency is just part of the equation.
>> You also have head movement times, which traditionally have been the
>> major part of time spent in a seek.
>
> For the Seagate drives, I see claims of less than 8.5ms average seek.

Just checked a local internet computer store, which mostly sell to 
private and small business. Seagate Cheetah. 15K rpm, U320 SCSI, 80 pin 
disk.
Average seek time is 3.5ms. 300GB disk. Costs about $500. (Noone said 
they were cheap.) 16MB internal cache on the disk.

>> 3600 RPM, by the way... That is the rotational speed of the RM03 (or was
>> it just 3000 RPM?). Also the RP04/05/06 if I remember right. Really old
>> disks... Sounds unlikely that todays small disks wouldn't spin any
>> faster than that.
>
> Not so long ago, though, 3600RPM was usual. As you note, you also
> have to include seek time in most cases, so making latency a lot
> less than seek time doesn't speed up access. On the other hand,
> at a fixed bit rate a faster rotation means less data capacity.

Right. But if you want higher bit rates, you might want to speed up 
rotation and maintain capacity. And the amount of data pushed through 
from a disk have gone up by a lot in the last 20 years...

	Johnny