SSH server Requirements

jaredscott · 11-05-2009, 06:34 AM

Hi guys

Please could someone assist me with a SSH query that I have

I plan on allowing 150-200 SSH connections to a Linux box and I was wondering what type of hardware and internet connection speed I would require

Each SSH connection will be transferring about 12kbps and although the maximum number of connections are 150-200, realistically I am sure that the server will only recieve about 80-120

Thanks in advance

choogendyk · 11-05-2009, 07:10 AM

hmm. You can do the math. You want a capability for a max 2.4Mbps. I don't see any reason why most hardware shouldn't be able to handle that, it's the network that's at issue, and the question is whether you are connecting from your home, a colo, or what? You're probably not going to be able to do it from home, unless you have a very unusual home setup. See http://en.wikipedia.org/wiki/Broadband_Internet_access for a summary of speeds of various kinds of connections.

jaredscott · 11-05-2009, 07:30 AM

Thanks for your response

That line speed should be very easy to achieve

Does anyone know how much RAM and CPU is needed per SSH connection (average)

choogendyk · 11-05-2009, 08:48 PM

According to top on my Sun server, I'm using about 5M+7M total size each ssh connection, but the actual resident memory varies and is less than that total. That's a root process and the user process (2 processes) that are spawned for each connection. If you have a Linux system, and have some ssh connections, try top. You can enter c while viewing top and then ssh, and it will show you just the ssh connections. Here's a sample from my Sun server:

Code:

   PID USERNAME LWP PRI NICE  SIZE   RES STATE    TIME    CPU COMMAND
 11557 user1      1  59    0 7424K 5264K sleep    0:00  0.00% sshd
  9491 user1      1  59    0 7424K 1488K sleep    0:09  0.00% sshd
 15429 user2      1  59    0 7424K 5336K sleep    0:01  0.00% sshd
  5519 user1      1  59    0 7424K 1808K sleep    0:01  0.00% sshd
 27151 user3      1  59    0 7424K 1792K sleep    0:01  0.00% sshd
  6583 user4      1  59    0 7552K 1648K sleep    0:01  0.00% sshd
 15428 root       1  59    0 5472K 3280K sleep    0:00  0.00% sshd
 11556 root       1  59    0 5472K 3112K sleep    0:00  0.00% sshd
  5597 root       1  59    0 4656K 1912K sleep    0:00  0.00% sshd
  5518 root       1  59    0 5472K 1080K sleep    0:00  0.00% sshd
 27150 root       1  59    0 5472K 1016K sleep    0:00  0.00% sshd
  6582 root       1  59    0 5472K  960K sleep    0:00  0.00% sshd
  9490 root       1  59    0 5472K  896K sleep    0:00  0.00% sshd

According to the top man page

Code:

     SIZE Total size of the process (text, data, and stack) given
          in kilobytes.

     RES  Resident memory: current amount of process memory  that
          resides in physical memory, given in kilobytes.

jaredscott · 11-06-2009, 01:27 AM

Thanks for that detailed response

Based on your report, I will budget 12MB of RAM per user, so if I need to support 150 SSH connections to my Linux box, I will need 1.8GB of RAM plus about 200MB for a light Linux OS, I am looking at about 2GB which shouldnt be a problem

Are there any other things that I should worry about if a single box is accepting 150 SSH connections? What type of processing power would I need?

Oh and I am hoping to run this solution on a fairly powerful VPS (virtual private server) in the states... I have been told that I should rather stick with dedicated machines but they are way more expensive... What are your thoughts?

Thanks

jaredscott · 11-12-2009, 03:33 AM

Hi

Can anybody assist with this query?

Thanks

choogendyk · 11-12-2009, 06:49 AM

I would think that most server class machines could handle that without too much trouble. I've never used a virtual server, but I presume they have service agreements that tell you what resources you are guaranteed and what you will be charged for based on usage.

I hadn't offered a comment before, because you wanted feedback on the virtual server question. If someone with firsthand experience with virtual servers could jump in with some examples, that might reassure you. Otherwise, since it's a virtual server, you could look into what the scaling options are for the service you are looking at. Can you easily ask for more resources (and pay more) if you find that your first attempt is inadequate?

jaredscott · 11-13-2009, 12:45 AM

Quote:

Originally Posted by choogendyk

they have service agreements that tell you what resources you are guaranteed and what you will be charged for based on usage.

That is correct

Quote:

Originally Posted by choogendyk

Can you easily ask for more resources (and pay more) if you find that your first attempt is inadequate?

The problem is that most VPS providers only sell them in tiers or in packages. For example, plan 1 could be 2.4GHZ, 512MB RAM, 60GB HDD and then the next one would effectively double all the hardware with the exception of the processor

This is all good and well, but unfortunately this means that the price jumps quite a bit as well and in most instances, the only reason why I would take a "bigger" plan would be to benefit from more RAM, nothing else. (So far, all the providers Iv looked at do not allow you to increase memory without taking on another plan)

It seems that if I need a lot of memory, the only way I am going to get it is to have a dedicated server, which means the entire box belongs to me (and not split up into multiple XEN/etc virtual machines)

But if I can grab a suitable VPS that has enough memory, is reliable and most importantly, offers a high level of PERFORMANCE for my product, then my problem is solved because VPS's are very affordable and flexible when it comes to growth

Has anyone had good/bad experiences using a VPS for their products?

Thanks for all the responses thus far