Minimum server hardware to fully use LAN bandwidth?

Minimum server hardware to fully use LAN bandwidth?

Post by n1jp » Thu, 11 Dec 2003 03:26:11


Situation:
I need a file server for data and OS backups on a LAN (100Mbps in this
case). Machine won't do any processing, and will do nothing but
standing by most of the time, so I'd love to go for the minimal
hardware (& power consumption, noise, heat, expense...).

Question:
Are there minimum CPU / controller / HD requirements for Samba to
saturate LAN bandwidth at 10 - 100 - 1000 Mbps?

Paraphrasing (+ guessed answers @ 100Mbps):
1- Would a P100 be enough? (guess: yes)
2- Would ATA33 or PIO33 be enough? In general, how does an ATA-XXX
spec translate into network interface erformance? (guess: PIO at 33
would be enough)
3- What about bus speed? Would it make sense to use a recent PCI
controller to put one or two large ATA100 or 133 EIDE HDs in an old
machine? (guess: not needed)
4- Once memory is enough to start all the relevant services without
using swap, does extra memory improve file serving performance at all?
(guess: little or no improvement, unless additional services are
tacked on later...)
5- Will any recent, large EIDE HD plug in & work properly in an older
machine? (guess: it should fall back to the available protocol, no
sweat; but power consumption could be high in modern 7200/10000rpm
units, so check PSU specs).
6- Other than specs, do NIC and other gear's chipsets / brands imply
different actual, repeatable bandwidth? (Guess: probably so. I have
seen the same NIC's negotiate different speeds or even fail to connect
on the same physical cable depending on the hub at the other end, even
if by the numbers the latter was identically configured and specced).

TIA to all. I hope this thread will be useful to others too.
 
 
 

Minimum server hardware to fully use LAN bandwidth?

Post by John-Paul » Thu, 11 Dec 2003 04:15:03

pamLover wrote:

I don't know how heavy Samba is in terms of processing power. I'm not
so sure a P100 will be able to handle the load of Samba, servicing disk
interrupts, and servicing network interrupts fast enough to saturate a
100Mbit link.

At 1000 Mbit (i.e., Gigabit) speeds, you need a *lot* of CPU just to
handle the network interrupts. Also, PCI bus bandwidth becomes a
bottleneck.


Remember that your LAN speed is in Megabits while disk speeds are
usually quoted in MegaBytes. So your 100Mbit/sec LAN connection has a
theoretical peak of 12.5MByte/sec. (Actual LAN performance will always
be a bit less.) You need a disk system capable of sustaining at least
that speed. ATA-33 is so-called because it supports a theoretical max
of 33MByte/sec. (Again, actual speed will usually be less.) Any fairly
recent disk and interface should easily outperform your 100Mbit network.


I concur with your guess if you're only using 100Mbit.


Caching data in memory can create an improvement in performance.
However, given your description of "standing by most of the time" I
suspect that data caching won't matter much under such a light load.


Actually, often times newer drives use less power and generate less heat
than older ones. I know of some people who claim their 18GB 10K RPM
SCSI drives use less power than the ancient 4GB 5400 RPM units that
originally came with their machines. Plus 7200 RPM will be your max.
(I don't know of 10K RPM units other than SATA, SCSI and FibreChannel.
I doubt you'll be using any of those in the box you've described.)


Yes. And performance can vary widely depending upon what's at the other
end of the link. For example, Brand X NIC may be fastest talking to
another Brand X NIC, but Brand Y wins when talking to a Brand Z switch.
Again, however, I'd suggest that given the light load you're describing
the performance difference isn't worth the trouble you'd spend trying to
optimize your network.

 
 
 

Minimum server hardware to fully use LAN bandwidth?

Post by Steve Wolf » Thu, 11 Dec 2003 05:01:11

> Are there minimum CPU / controller / HD requirements for Samba to

I can't say for sure, but my guess is that the Samba processing may get
to be a bit much for the P100, especially when you have several people
hitting it at once. I'm going to confine the rest of my message to 100
mbit operation, trying to get full gigabit operation out of a Samba server
will take far more hardware power than you seem to want to throw at it.
; )


There is no PIO33, but PIO modes 1, 2, 3, and 4. PIO modes use MUCH
more CPU than DMA modes, So the P100 may very well not be enough.

I've seen low-power machines used as succesfull file servers, when used
with good-quality SCSI disk systems. SCSI systems require next to no CPU
for disk I/O, leaving the CPU free for the Samba layer and networking.


It can, by keeping the most-used data in cache. If your disk system is
very slow and your CPU is very anemic, that can make a lot more difference
than if you have fast disks and powerful CPU's.


Chances are that it won't, especially not on a machine as old as a P100.
*If* you put a newer controller card in, then your chances are much
better.


There are a lot of cheap NIC's that don't have much implemented in
hardware, and take more CPU than others. Using a higher-quality NIC would
probably be a good idea.

Despite the fact that more modern processers have reputations for being
power-hungry, that's not entirely true. The original Pentium line of
CPU's had a power dissipation of 10.1 to 15.5 watts, with your P100
probably falling around 11 to 11.5 watts. The Intel Celeron "II" (FC-PAG)
line (533 MHz to 766 MHz) had a power consumption range of... 11.2 to 23.6
watts. That means that you could have a 533 MHz Celeron (Coppermine core)
with on-die, full-speed cache and a lot more computing power for the same
electrical budget, which would not only give you much more CPU power,
you'd also get much more modern disk controllers on the motherboards in
question, easing several of your constraints. Plus, it just might have
better power-saving features as well!

steve
 
 
 

Minimum server hardware to fully use LAN bandwidth?

Post by n1jp » Sun, 14 Dec 2003 08:46:13

Thank you guys!

Very informative + dispelled a few incorrect notions!

Filippo