Hi all,

so I have just assembled my first unRAID build and all seems to be working fine. I have an AMD A6-6400 cpu in the system and I am wondering if upgrading this to the A10-6800 would help with the server in any way? (Parity-Sync speed?)

The box is going to be mainly used as a Plex Media server and for the most part will be doing direct play over the network.

 

One other non-cpu question, if I removed all the hard drives from an unRAID setup, did a fresh unRAID install and then added those drives back into the box, would unRAID detect their original configuration from the old setup or would it want to perform a full new array setup and hence lose all the data on those drives?

 

Thanks in advance for any help or advice.

Question #1. For your intended usage, concentrate on I/O and not chip speed.

The real speed constraints are most likely to be your LAN-Speed, parity writing and Hard-drive speed. 

In my humble opinion, in order of 'cost effectiveness and impact', upgrade a system as follows:

• RAM (2Gig works, 4 is better, 8 if you have lots of plugins).
  
• LAN (use a modern Gigabit speed ethernet switch to connect the primary computer, router and unRAID box).
  
• CACHE drive. Buy the Pro key to unRAID and install a cache drive. This typically doubles WRITE speed to unRAID, (no impact on Read)
  
• FASTER Hard Drives (7200 RPM read and write 25% faster than 5400 RPM drives, all else being equal) (and even here, the DATA drives don't need to be 7200, parity and Cache can really benefit)
  

IF you're running lots of plug-ins, with heavy CPU usage, then maybe

• RAM (8 GIG helps)
  
• CACHE drive. An SSD will help on write speed, and for certain programs which write a great deal such as torrents.
  
• CPU if you are doing heavy calculations. If you are transcoding video from the stored unRAID format to iPad, phones, TV,etc., and you're doing it in real time on the fly,  then a fast enough CPU is needed. Even then, this can be worked around by just saving files in several different formats--PLEX will automatically pick the best format for each device.
  

For comparison, my unRAID box has an Intel i5 chip--That chip has a PassMark speed score of about 3100 versus the AMD of 2400.  I've never seen my Intel i5 go over 15% on CPU usage...turns out that I could have saved some money.

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Question #2. Starting all over:

UnRAID keeps track of which drive is Parity, which is Data, etc., by using the drive Serial Numbers. Port numbers can change from boot to reboot, but the drive serial numbers are the critical data.

You could reuse the config file on your existing flash drive. (just copy it to your PC) and copy it over to your next flash. BUT, the smart guys on the forum told me to instead take and save a screen shot of the WEB GUI showing the Drive Serial Numbers of the current working configuration. Assuming you're reusing all the same hard drives, there are TWO drives that are critical, Parity and Cache.  When you rebuild your array, BE SURE that you Assign the same Parity Disk. If you had a cache drive, be sure you assign the same Cache Drive. The order of the Data disks doesn't matter, as long as they are all 'data'.  Bring the array back online, and ensure everything checks out using the new key.

 

So for the first part of your reply, I have 8gigs of memory and also 1gigabit connections on my network except for a Roku client which is wireless and also some laptops which are wireless at 130mbps speeds.

 

From your response it sounds like the cache drive would alleviate any transcoding bottlenecks on the unRAID server. I am not running any other plugins on the server and most likely will not run any on it.

From your response it sounds like the cache drive would alleviate any transcoding bottlenecks on the unRAID server.

 

Not necessarily.  Transcoding can be a very CPU-intensive operation.  It's the one function where a higher-speed CPU would benefit.    All of the NAS-related functions (reading, writing, parity checks, drive rebuilds, etc.) are very low CPU-utilization operations, and wouldn't benefit from a higher-speed CPU, but Plex definitely would ... especially if you plan to support multiple simultaneous transcodings.

 

A couple comments on the above post ...

 

... install a cache drive. This typically doubles WRITE speed to unRAID ...

 

A cache does indeed enhance writes -- with modern drives and Gb networks it typically triples the speed.    But be aware that anything written to the cache is not fault-tolerant until the mover script moves it to the protected array.    It does, however, make a nice application-only drive for internal apps that need workspace where you don't care if you lose the data if the drive fails.    Dirtysanchez posted a nice script that you can use to backup your application folders to the protected array on a scheduled basis -- this mitigates the loss of things like a large Plex database, etc. if you're keeping them on the cache drive.

 

 

... 7200 RPM read and write 25% faster than 5400 RPM drives, all else being equal ...  (and even here, the DATA drives don't need to be 7200, parity and Cache can really benefit)

 

In general, this is simply not true if you're using modern 4TB drives.  No manufacturer has released a 7200rpm 4TB drive with the same areal density as their NAS units.  The NAS units (both Seagate and WD Reds) use 1TB/platter drives; but all of the currently shipping 7200rpm 4TB units are 5-platter 800GB/platter drives.  So even though they're spinning faster, the slower NAS units provide 25% more data/rotation.    The 7200rpm units DO have an access time advantage ... so for multiple small reads or writes they tend to be a bit quicker; but for streaming, the NAS units can easily keep up due to the higher areal density.    The simple fact is that either unit can saturate a Gb network, so the effective performance is the same with both.

 

A 7200rpm unit for your parity drive will provide marginally better writes if you're doing a lot at the same time (due to the better access time); but isn't likely to help with parity check speeds in an all 4TB drive system.    A 7200rpm cache drive is beneficial, since most cache activity is going to be relatively small writes and the better access times will help ... but quite candidly if you want the best cache performance, I'd buy an SSD.

 

So is there a way in UNRAID to monitor the cpu so that I can confirm how it is being stressed during real time transcoding?

 

Sent from my SM-N900V using Tapatalk

 

 

Install UnMenu; go to the UnMenu page, click on System Info, and then on Top Processes.    This will show the CPU % being used by those processes.

 

Cool, thanks

 

Sent from my SM-N900V using Tapatalk

 

 

If you are upgrading for the purposes for gaining transcoding speeds in Plex then reconsider using the A-series processors and instead go for the FX line.

 

But more generally, buy the CPU with the highest passmark score you can for the money you have allotted.  Plex transcoding speed (in fact anything using ffmpeg really) scales with passmark score very cleanly.

 

All that said, if you are mostly direct streaming then a faster CPU will be of no use to you.  For occasional transcoding, like raw BD rips or remote streaming a single stream, your cpu should be able to handle the job just fine.  Going faster will do nothing useful for you really. The A6-6400 scores 2400 on passmark which is good for just under 2 full streams based on the assumption that you need ~1500 for a single stream.