Questions about hardware and performance

[coppit]

Hi all, I'm considering building an unRaid server and have some questions:

 

• I don't understand why a 2+ GHz CPU is recommended. I would think that an I/O intensive system like this could get by with < 1 GHz CPU?
  
• Ditto for memory. Why is more than 512MB needed?
  
• I'm was hoping to stream 2 HDTV recordings from SageTV to it, but people on the SageTV forums are saying that I'll get dropped frames. Is there any hope for better write performance in the future? (Is it just a matter of waiting for faster disks, or making sure I buy fast disks now?) BTW, I plan on using gigabit ethernet between the machines.
  
• Has anyone found a suitable pre-built OEM system, rather than assembling it themselves? I was hoping for a Walmart or Newegg machine that would be cheaper than buying all the parts separately.
  

 

[coppit]

To answer my own questions (please correct me if I'm wrong):

• I don't understand why a 2+ GHz CPU is recommended. I would think that an I/O intensive system like this could get by with < 1 GHz CPU?
  

 

All the RAID is implemented in software, which requires some CPU to execute lots of XORs compared to hardware RAID solutions. Plus 2.5 GHz CPUs are about $60, so why not?

 

• Ditto for memory. Why is more than 512MB needed?
  

 

We can get by with 512MB. Two sticks of 512MB for DDR is really not necessary. (Right?)

 

• I'm was hoping to stream 2 HDTV recordings from SageTV to it, but people on the SageTV forums are saying that I'll get dropped frames. Is there any hope for better write performance in the future? (Is it just a matter of waiting for faster disks, or making sure I buy fast disks now?) BTW, I plan on using gigabit ethernet between the machines.
  

 

Some people have had success writing two HDTV streams at once while reading another. Try it and see.

 

• Has anyone found a suitable pre-built OEM system, rather than assembling it themselves? I was hoping for a Walmart or Newegg machine that would be cheaper than buying all the parts separately.
  

 

I ended up grabbing all the parts (minus drives) from Newegg for a few hundred. Not too expensive...

[limetech]

Good questions and answers!

 

I would add the following:

 

- Yes main reason for 2GHz CPU is because it's cheap, so why not?

- Either 2 sticks of "slow" memory operating in dual-channel mode, or 1 stick of "fast" memory.

 

[TheMaster]

coppit -

 

You may want to check out my post "ULTIMATE UNRAID SERVER?".  You will see there is a dramatic variation in transfer speeds between different configurations of UNRAID.  The server I recently put together will rival any NAS on the market for performance, so I believe you will be able to perform the 2 parallel HD feeds if you setup your server appropriately.  There are several benchmarks in that thread for your comparison.

 

Definitely second the moderator's recommendation for dual channel memory.