[OT] hardware setup: network speed and raid...

[chriss]

hey guys

a while ago some people over here were discussing server issues and i followed this topic with great interested. there seemed to be a lot of people with good knowledge about network setups so i figured i should ask over here about this problem...

some friends of mine are working together on three Mac Pros connected to a G5 computer. the g5 functions as a server and has 3 hard drives via firewire attached. now the three are often transferring gigabytes of data from and to the server. the speed is horrible and this is just no solution for the future... but what woud be a better solution? something like an upgrade of the current setup that doesn't cost too much...

i told them they should get a PCI-X card like this one (the g5 is quite old so it doesn't support pcie yet). i thought best would be to then set up a raid5 system to speed up the connection!

but i think the external hard drives are probably not the only bottleneck of their setup.

is there a way to speed up the lan speed? does it make more sense to have all 3 computers connected individually to the server? do you guys think the g5 could be to old to function as a good server?

thanks for any help

[bkenobi]

I can't say for sure where the problem in the setup lies. However, there are a few places bottlenecks can occur in general. First, make sure your router is actually gigabit. I have not seen many routers that are, so I actually use a gigabit switch to split out my connection between all my computers. The wireless router is connected to the cable modem and then on to the switch so that I can share my connection to laptops on the network. Also, your router might not be capable of dealing with the number or type of packets that are being sent. Some network devices can support "jumbo" packets. I don't really understand all the details with them, but lets just say if your router doesn't support these, the connection can get bogged down. Be aware that the newtork itself can only support a total throughput (meaning, each device can't transfer gbps all at the same time). I can't say a damn thing about the computer as I'm not familiar with Mac's hardware and software at this point. BUT, the connection to the router could be a big bottleneck. If so, you can add more network cards to the server to allow higher throughput. If you do that, you may need multiple routers/switches (I haven't had this issue, so I haven't looked into it). The final bottleneck could be the firewire drives. I would look into this last, but it can be tested easily since you can just transfer the same file from one drive to another and time it.

When I was building my server, I spent a lot of time testing different bottlenecks and found that all local drives (including USB and Firewire) were faster than the network (even up to GB). Hope that helps. If not, there are a TON of resources available to help with this problem! Just check out google for a few.

[chriss]

thanks bkenobi, as always

i'll have a chat with my friend tomorrow and tell him about your thoughts. It sounds like a good router is the key to success! Do you happen to have a link to a good guide of setting up a server? i found tons of stuff on google but is there a recommendation from your site?

[bkenobi]

There was a site I used that I can't remember now. It was something like "network peripherals", but that's not it. Anyway, I always recommend Tom's Hardware. I just checked their forums and found over 60,000 threads in the general networking discussion area. I had a problem with my PC last week and I was able to get help VERY quickly (a USB device had locked up and kept my system from POSTing...didn't know USB could do that). Anyway, they would be my first stop.

[chriss]

yeah tomshardware is awesome! good call!

[papazark]

When I was building my server, I spent a lot of time testing different bottlenecks and found that all local drives (including USB and Firewire) were faster than the network (even up to GB).

Hi there

I've done some speed tests on my setup using RAM Drives on 2 machines (2 Vista ) and I was able to transfer at about 125 Mb/s (network usage at 100% in the taskmanager, and actual transfer duration confirmed it), but I was never able to reach that speed with 'single' conventional harddrive. So in my case, the drive speed is the bottleneck.

What usb drives were you using to be faster than a Gigabit network ? were you RAIDing your drives ?

[bkenobi]

Be careful with MBps and Mbps. There is a big difference. When manufacturers list the throughput speed, they list "gigabit" or "1000 mbps" which is not what you think. In reality, you will see ~10% of what you expect due to marketing and such. I found that I can achieve ~50 MB/s on my gigabit network by transferring from one device to another with short cables and a gigabit switch (no other devices). I tried MANY configurations and some were much slower.

I thought I had deleted all of my testing, but I guess not. I still have the results, so I can post what I used and you can try it yourself.

Read this page first:

http://www.smallnetbuilder.com/index.php?option=com_content&task=view&id=24310&Itemid=77

Then, use iozone (www.iozone.com) with the following command:

iozone -Rab Results.wks -i 0 -i 1 -+u -f e:\tmp.tmp -q 64k -n 32M -g 1G -z

where,

• "Results.wks" is an output file where iozone puts the results in M$ Works format
  
• "e:\tmp.tmp" is the location of a test file iozone will create
  

The command is described in the article nicely.

[Endaar]

I'm going to partially disagree with bkenobi here...Without seeing the setup in person, I really doubt network speed is the problem unless all three users are literally copying huge files simultaneously. Even at that, I suspect your drives would be the bottleneck way before the LAN. IDE drives aren't exactly the best for random access by multiple users.

Honestly though, this shouldn't be all that hard to figure out. When you have slowdowns, what is the server's CPU utilization, and what is the network utilization? If both are acceptable - under 80% let's say - that would point to the drives.

The other thing as bkenobi mentioned is whether the router is actually a Gb unit. Also, if you have port speed and/or duplex hard-coded on one side of a link and set to auto on the other, you will see a lot of packets dropped which can kill transfer speeds. Ideally, set everything to auto on both ends of each link.

Endaar

[bkenobi]

It's definitely hard to tell what's the bottleneck...which is why I suggested testing. I did a TON of testing and found that, in my setup, the bottleneck wasn't the drive speed, it was the network. That doesn't mean that's a universal though. I'm not an IT expert, so I don't have a solution other than testing and trying different things. Actually, my gigabit speeds are a bit slower than I had hoped for to this date. I got things fast enough that I was happy with them and moved on (since I didn't want to become an IT expert).