I currently have a Celeron D 333 2.8Ghz processor in my unRAID, but I've got a spare Pentium D 920 2.8Ghz processor laying around. CPU benchmarks show the Pentium has about twice the performance of the Celeron.

 

I've currently got a 13 data disk + parity + cache drive setup and use it mostly for video streaming. I think the only program that runs in the background is the cache_dirs utility.

 

So my question is, is it even worth the effort to upgrade the processor, or will it make absolutely no difference?  I'm guessing the array writes are hard drive limited rather than processor parity limited, right?

It will not make a difference in enhancing unRAID's performance.

More memory can help (up to 4GB).

 

I would not change the processor unless I was going to run VMWARE guests

or

Change it to a lower power processor (even a celeron M can run unRAID and save electricity).

Thought as much, but wanted a second opinion, thanks WeeboTech.

 

My MB is maxed out at 2GB memory.  Hmm, come to think of it, I may have another MB laying around that would support more. Need to check that out.

I currently have a Celeron D 333 2.8Ghz processor in my unRAID, but I've got a spare Pentium D 920 2.8Ghz processor laying around. CPU benchmarks show the Pentium has about twice the performance of the Celeron.

 

I've currently got a 13 data disk + parity + cache drive setup and use it mostly for video streaming. I think the only program that runs in the background is the cache_dirs utility.

 

So my question is, is it even worth the effort to upgrade the processor, or will it make absolutely no difference?  I'm guessing the array writes are hard drive limited rather than processor parity limited, right?

You can see for yourself by typing

top

 

at  the command line.  (press the letter "q" to quit)

 

The "cpu" usage is at the top of the screen updated every few seconds.

The first two columns are user-space programs, and kernel space processes.  %wa is time waiting for I/O

%id = %idle.

When doing a parity check on my system with 10 disks, worst value I saw is 75%idle.  (25% in kernel processing)  I've got an old Celeron cpu.

 

You are correct in that array "writes" are limited by the hard disks.  To do any "write" unRAID must first "read" the current contents of a sector and then write the replacement.  The rotational speed of the disk determines the overall write rate.  A faster CPU will not get the disk to spin faster to get around to the same sector for the "write" after reading it.

My MB is maxed out at 2GB memory.  Hmm, come to think of it, I may have another MB laying around that would support more. Need to check that out.

 

It may not even be worth the effort.

If unRAID is just a file server and you have 2GB you are fine where you are.

 

If you plan to run rtorrent or install a number of addon packages, then the extra ram comes in handy.

 

Yeah, I agree it's not worth it.  Especially since my spare MB doesn't have onboard video so I'd have to add a GPU as well.  I've got a spare one of those too, but...

 

Thanks for the help!

My unraid doesn't have any extra scripts or programs installed on it. Stock unraid.

 

I only have 1GB of memory installed and everything seems fine. I have around 3 Terabytes of Storage. Blurays etc stream fine.

 

RAM is so cheap I will add another stick if someone can explain how I will benefit. 4GB seems like it would never be utilized.

 

My unraid doesn't have any extra scripts or programs installed on it. Stock unraid.

 

I only have 1GB of memory installed and everything seems fine. I have around 3 Terabytes of Storage. Blurays etc stream fine.

 

RAM is so cheap I will add another stick if someone can explain how I will benefit. 4GB seems like it would never be utilized.

 

 

If you have not felt the need to upgrade in preventing spurious disk spin ups, then the extra ram will be utilized, but the return on investment will be nil.

 

The kernel will always cache as much data until it needs to release old data.

so the ram will be used, but my be flushed out by reading another file before it is even noticed.

 

Generally people put the extra ram in the system so that directories are cached.

This alleviates spin ups of disk that you are not intentionally targetting.

 

For example.

If you have 10 disks in a Videos share.

On low ram. a directory search for a file on Videos may cause the user filesystem to spin up each disk just to provide a directory.

 

With Joe L's cache_dirs script, it causes many directories to stay in ram without expiration.

 

This help sthe user share file system read a directory without spinning up a disk, because the directory is already in memory.

When would I directly see the benefits of directory caching?

When would I directly see the benefits of directory caching?

 

it's based on your usage patther.

 

How many disk drives.

How many files,

How many workstations,

and how often each workstation searches for files.

 

There is no hard and cllear fast rule for this.

 

unRAID machines were built with 512MB for a long time.

 

Recently users are adding more and more to unRAID and the usage patterns cause disk spin ups.

If the time it takes to wake up disks has not been noticed yet, then the extra ram will not be needed.

A brief pause when selecting a movie on xbmc happens if they aren't spun up. But it is a 5 second wait until the movie starts. Not a big deal.