Resource Requirements for UCx Virtualized Software

Capacity Considerations

There are four variable criteria that need to be considered to successfully deploy a UCx virtualized software:

  1. Amount of memory (RAM)
  2. Size of the persistent storage (HDD or SSD)
  3. CPU processing power
  4. IOPS (drive I/O operations per second)

The required criteria for these four variables can be computed based on four pieces of information from the customer:

A - The absolute maximum number of users ever expected on this system
B - The maximum number of hours of voice storage per user
C - The maximum number of hours of call recording storage
D - The maximum number of concurrent calls

The following subsections will describe how each of the four criteria are calculated.


The following table lists the recommended memory required based on the number of users.

Number of users Memory Required
0 - 100 users 2 GB
101 - 300 users 4 GB
301 - 500 users 6 GB
501 - 700 users 8 GB
701 - 1000 users 12 GB


For number of users exceeding 1000, please contact your E-MetroTel representative.

Persistent Storage (HDD or SSD)

The following table provides the recommended storage requirements based on a few sample deployments.

Number of users Number of hours of voicemail storage per user Number of hours of Call Recording storage Recommended Storage
25 2 hours 1000 hours 32 GB
80 2 hours 2400 hours 60 GB
450 2 hours 7000 hours 200 GB
1000 2 hours 16000 hours 500 GB

The following formula can be used to calculate the specific storage requirements for the customer:

  1. ​Minimum base storage = 16 GB
  2. Voicemail storage = (number of users) x (number of hours of voicemail storage per user) x (60 MB)
  3. Call Recording storage = (number of hours of call recording storage) x 8 MB

Total up the above three storage calculations to arrive at the minumum storage required for your UCx Server.

Processing Power (CPU)

The following table lists a few common CPU models based on the number of concurrent calls. (Benchmarking data provided by:

Maximum number of Concurrent Calls Minimum PassMark Intel CPU AMD CPU
0 - 50 1250 Intel Core i3-370M @ 2.40GHz AMD A8-4500M APU
51 - 100 2000 Intel Core i3-370M @ 2.40GHz AMD A8-4500M APU
101 - 250 4250 Intel Core i5-2400 @ 3.10GHz AMD A10-5800K APU
251 - 500 8000 Intel Core i7-2600 @ 3.40GHz AMD FX-8350 Eight-Core

The PassMark CPU benchmark is used to estimate how quickly a processor is able to perform a wide variety of calculations. The faster the processor is able to complete the tasks, the higher the PassMark rating.
The following formula can be used to compute the minimum CPU required using PassMark scores:

  1. Minimum CPU PassMark rating = 500
  2. Additional CPU PassMark rating = (number of concurrent calls) x (15)

Total the above two ratings to obtain the minimum required PassMark rating for the CPU.

For number of concurrent calls exceeding 500, please contact your E-MetroTel representative.


A mechanical Hard Drive (HDD) can support approximately 175 IOPS.  An SSD can support well over several thousand IOPS.  The system will need 2-4 IOPS for each concurrent call that is being recorded (Voicemail or Call Recording). 
Using SSD is recommended. If using HDD, get the fastest drive with a high reliability for 24/365 usage. Drives marketed for Data Centers work well.

The following table provides a sample of the required IOPS that the drive must support based on the number of concurrent call recordings.

Number of concurrent call recordings Required IOPS
0 - 20 80
21 - 50 200
51 - 100 400
101 - 250 1000
251 - 500 2000


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