How much RAM should I use?

[jebusfreek666]

So here is a quick run down of the parts I have on hand for my build. I was originally planning and buying parts for a FreeNas build, but Unraid seems to fit my needs better. I am currently planning to use this server primarily as a media/plex server. There is a possibility of 4 simultaneous transcodes (although this will be exceedingly rare). It is more likely that this will be used most of the time in house with hard line, and maybe 1-2 outside streams at other times. And I am looking at converting all my media over to MKV to avoid tanscoding issues. I will be running docker (once I read up on it and understand it a little better) for all the necessary media gathering/sorting/playing programs.  I may dabble in VM later on, but I don't game or do any video editing or anything like that. At most, I was thinking it would be kind of cool to setup VM so the kids could have access to "windows" machines on their chromebooks, if this is even a possibility. Also, I have been getting into home automation, so this might be something I migrate to the server if I get more involved/advanced with it. Currently, I don't even have a hub though. Just running Lutron caseta and Philips Hue bridges with alexa. But this could conceivably be expanded later on.

 

Processor: Intel Xeon Processor E3-1230 v5

MOBO: Supermicro Micro ATX X11SSM-F-O

RAM: SAMSUNG M391A2K43BB1-CPB DDR4-2133 16GB ECC (64GB total)

PSU: Seasonic SS-660XP2 ATX 12V / EPS 12V, 660W, 80 PLUS PLATINUM

HDD: Toshiba X300 6TB (8 of these)

SSD: Samsung Evo 850 500GB (2 of these)

Define R5 Case

 

The more I look in to it, the more it seems to me I have an excessive amount of RAM. So I am thinking I might just use 1-2 sticks (16-32GB, though leaning towards 32GB). I was thinking about possibly using the other 2 sticks in separate builds, to have off-site back up servers at my mother and sisters house to back up my actual important data (photos, documents). They could also use these as mini-media servers in their homes.

 

So my question is, would it be better to use just 16-32GB of ram? Would the full 64GB be a waste for me?

 

Also, dumb question, my MOBO has 4 RAM slots. 2 black, 2 blue. I know that this is "dual channel", but I am not 100% clear on what this entails. If I do use only 2 sticks instead of all 4, should I populate 2 of the same color or one of each color to maximize their effectiveness?

 

Thanks for all the help!

 

Edited January 22, 2018 by jebusfreek666

[JorgeB]

16GB would be enough, maybe 32 for multiple VMs, for dual channel use 2 slots of the same color.

[SSD]

You can use unRAID to transcode to RAM, which is a nice feature. 64G may be more than needed, but might need to experiment. Memory is needed when using VMs, unlike with Dockers, VM memory has to be dedicated to the VM. So if you are running 2 Windows VMs, and want each to have 12G of RAM, that is 24G RAM gone that neither Plex nor anything else can use.

 

Regarding memory installation order - RTFM

 

https://www.supermicro.com/products/motherboard/Xeon/C236_C232/X11SSM-F.cfm, click Motherboard manual link, download the PDF, page 34.

 

 

[SSD]

1 minute ago, johnnie.black said:

16GB would be enough, maybe 32 for multiple VMs, for dual channel use 2 slots of the same color.

 

This is different than the advice given in the manual. They have a specific slot load order defined.

[JorgeB]

21 minutes ago, SSD said:

They have a specific slot load order defined.

Yes, IIRC blue slots first are recommended but it will work with either.

[jebusfreek666]

Awesome. Thanks for the link! I'm going to read the whole thing now. Thank you both for all the help you give to me and everyone else! I am sure I will be back soon to further my education.

[jebusfreek666]

2 hours ago, SSD said:

You can use unRAID to transcode to RAM, which is a nice feature. 64G may be more than needed, but might need to experiment. Memory is needed when using VMs, unlike with Dockers, VM memory has to be dedicated to the VM. So if you are running 2 Windows VMs, and want each to have 12G of RAM, that is 24G RAM gone that neither Plex nor anything else can use.

 

Regarding memory installation order - RTFM

 

https://www.supermicro.com/products/motherboard/Xeon/C236_C232/X11SSM-F.cfm, click Motherboard manual link, download the PDF, page 34.

 

 

I am having a hard time seeing a point to using RAM for transcoding. Just spent a little time reading up on it, and it seems like a neat concept but not really a necessary thing. I can't imagine it will save that much life on the SSD in the long run. And I am sure I will want to upgrade long before that. You mentioned dedicating RAM to VM's. If you were running a basic windows VM, not anything intensive. Mostly just word processing, maybe some smaller stuff, would you dedicate the same amount of memory as physical computer? What I mean is, if there is no gaming, would it need 12GB RAM? Since most cheap budget laptops survive with 4-8GB, would that also be sufficient for a very basic VM? Also, do you have to dedicate cores/threads to a VM as well? I have seen that it can help, but is it necessary?

[JonathanM]

Keep in mind that a VM needs RAM from the host to manage the emulated hardware. So, if you allocate 8GB of RAM to the VM, the actual host RAM usage while the VM is running is probably closer to 10GB. Unraid itself needs about 4GB of RAM to be comfortable, so 16GB of RAM would be comfortable for 1 VM at a time. You don't have to dedicate threads to the VM, but you do allocate thread preference. You CAN exclude threads from unraid's use and lock them to the VM if you want, but that is more advanced and not a GUI option.

[SSD]

2 hours ago, jebusfreek666 said:

I am having a hard time seeing a point to using RAM for transcoding. Just spent a little time reading up on it, and it seems like a neat concept but not really a necessary thing. I can't imagine it will save that much life on the SSD in the long run. And I am sure I will want to upgrade long before that. You mentioned dedicating RAM to VM's. If you were running a basic windows VM, not anything intensive. Mostly just word processing, maybe some smaller stuff, would you dedicate the same amount of memory as physical computer? What I mean is, if there is no gaming, would it need 12GB RAM? Since most cheap budget laptops survive with 4-8GB, would that also be sufficient for a very basic VM? Also, do you have to dedicate cores/threads to a VM as well? I have seen that it can help, but is it necessary?

 

Yes - a lightweight Windows VM with 4G of memory might be possible. 12G was just an example. As @jonathanm points out there is overhead for unRAID to run the VM. You can experiment to find out. I usually like 16G-32G for a VM - but I am not a casual user. 

 

The key point is that VM memory is not shared and usable by unRAID or Dockers when not used by Windows. (Cores can be shared.) I do think you could make it work with 32G of RAM, which is a very generous quantity, but you have to think through how you want to allocate it. Transcoding to RAM is not a huge RAM requirement and obviously has performance advantages.

[wayner]

17 hours ago, jonathanm said:

Keep in mind that a VM needs RAM from the host to manage the emulated hardware. So, if you allocate 8GB of RAM to the VM, the actual host RAM usage while the VM is running is probably closer to 10GB. Unraid itself needs about 4GB of RAM to be comfortable, so 16GB of RAM would be comfortable for 1 VM at a time. 

This is getting way OT, but talk of this much memory makes me shake my head when I think back to the first PC I bought - a Commodore VIC-20 with 3.5 kiloBytes of memory.  We are now wondering if over 4,000,000 times that amount of memory is enough.  Sure, computers do a lot more than they could in 1981 but this is incredible!

[SSD]

In the early days, memory was constrained and programmers were very conscious of those limitations. Early DOS had 64K memory! Today programmers think they have infinite memory! And they almost do! 

 

But in the old days, there were no GUIs, files were measured in KB and not GB. Disks are MB not TB. A lot has changed! 

 

As I tried to say, 32G is a generous amount. If you said you were going from 16G to 32G, we'd all be saying great. But it gets harder to recommend to reduce memory. As people are always thinking of more. If you give it up, you may have regrets. Think realistically about what memory you need in your VMs, be it 4G/6G/8G or more. Try it and tweak if there are complaints. And if you need more, you can get more. But 32G is more than ample IMO.

[wayner]

17 minutes ago, SSD said:

In the early days, memory was constrained and programmers were very conscious of those limitations. Early DOS had 64K memory! Today programmers think they have infinite memory! And they almost do! 

I know - my excuse for not commenting code is that when I learned to program, bytes were too valuable to waste on non-functional code.