Editing VM CPUs and RAM

Virtual machine hardware settings determine the amount of Metered RAM and CPU capacity that the VM consumes—larger VMs consume more Metered RAM and CPU capacity. For information about how Metered RAM and CPU capacity are calculated, see How usage is calculated.

Contents

Instructions

To edit the VM CPU and RAM settings
  1. Make sure the VM is fully powered off (not running or suspended).
  2. Before making hardware changes to your VM, create a template of it. If any problems occur, you can restore your VM from this template.
  3. Navigate to the VM Settings > Hardware page.

    hardware settings

  4. Next to CPUs, select the number of CPUs that the VM will use.

    If an x86 VM is hardware version 10 or newer, click Advanced to see multi-core CPU options. By default, Skytap configures 1 CPU core per socket.

    Notes

    • The maximum number of CPUs for a single VM varies, depending on region. For a list of regional capabilities, see Skytap Cloud features by region.
    • If an x86 VM is hardware version 9 or earlier, you can upgrade the VM hardware version to make advanced CPU configuration options available. For instructions, see Upgrading VM hardware versions.
    • The number of cores per socket must be 1, 2, 4, or 8. Only valid CPU configuration options are displayed.

  1. For AIX and Linux on Power VMs, set CPU sharing mode to either Uncapped or Capped.

    • Capped – The VM can never exceed the entitled capacity, determined by the CPUs and RAM values for the VM.
    • Uncapped – The VM will automatically use any excess processor resources available in the shared resource pool, in excess of the entitled capacity. This is the default setting.

    CPU sharing mode helps control costs for applications that determine license cost, based on vCPU usage.

  2. Next to Hardware RAM, enter The amount of RAM (in MB) that the VM will use.

    Notes

    • The amount of ram (in GB) must be equal to or greater than the number of CPUs.
    • The maximum amount of RAM available for a single VM varies, depending on region.
    • For x86 VMs – Increasing the amount of RAM, also increases the IOPS performance (up to 16 GB of RAM).
    • For Power A CPU architecture that supports IBM i, AIX, and Linux (on Power) in Skytap Cloud. VMs – Increasing RAM enables higher Entitled capacity (effectively increasing CPU performance). For specific details, see the CPU Entitled capacity lookup table below.
    • For Power VMs – The minimum supported RAM is 2048 MB (2 GB).
  3. If you want to limit Entitled capacity for a Power VM to a value lower than that calculated by CPUs and Hardware RAM, click edit and type the Entitled capacity value you want to use.

  4. Click Save.

Additional information

  • Follow vendor recommendations for the operating system and the installed applications when setting the CPU and RAM values. Generally:

    • Additional CPU cores permit more concurrent system and application processes, which improves system performance.
    • Additional RAM allows more applications to be active and improves access speeds for data.
  • Some VMs may not support every configuration option that Skytap allows you to set. The guest OS type and hardware version number determine the amount of CPUs and RAM that a VM can use.

    For example:

    • Windows Server 2008 R2 Standard VMs support a maximum of 4 CPUs. If you select 8 CPUs, 4 of those CPUs are ignored by the guest OS.
    • VM (x86 The most common CPU architecture. x86 CPUs support Windows and Linux VMs in Skytap Cloud. ) hardware versions 9 and earlier don’t support 12 CPUs or 256 GB of RAM. For example, if you select 12 CPUs for a VM on hardware version 7, you may see an error message when the VM runs.

These tables provide GB-to-MB conversion values for common RAM settings.

GB MB   GB MB   GB MB   GB MB
1 1024   9 9216   24 24576   192 196608
2 2048   10 10240   32 32768   224 229376
3 3072   11 11264   48 49152   256 262144
4 4096   12 12288   64 65536   320 327680
5 5120   13 13312   80 81920   384 393216
6 6144   14 14366   96 98304   448 458752
7 7168   15 15360   128 131072   480 491520
8 8192   16 16384   160 163840   512 524288

You can copy the MB value you want and paste it directly into the Hardware RAM (MB) field on the Hardware tab of the VM Settings page.

For Power VMs, set Entitled capacity (and approximate IBM i CPW) by changing the amount of RAM and the number of CPUs.

The table below was calculated with the following formulas:

  • EC=MIN(vcpu_count,FLOOR(MAX(gb_ram/40,0.05),0.01))
  • vcpu_limit=MIN(ROUNDUP(EC*20,0),16)
  • CPW=EC*10618 (approximation)

Notes

  • This table provides some common RAM and CPU core combinations for Entitled capacity and CPW. You can choose other values for both RAM and CPUs—the updated Entitled capacity value displays in the Skytap interface.
  • The Entitled capacity (and approximate CPW) values in this table are guaranteed when the corresponding RAM and CPUs are configured for the VM.
CPU Cores
1234
RAM EC CPW * ECCPW * EC CPW * EC CPW *
1 GB0.05 530 --- --- --- --- --- ---
2 GB0.05 530 --- --- --- --- --- ---
3 GB0.07 7430.07 743--- --- --- ---
4 GB0.10 10610.10 1061--- --- --- ---
5 GB0.12 12740.12 12740.12 1274 --- ---
6 GB0.15 15920.15 15920.15 1592 --- ---
7 GB0.17 18050.17 18050.17 18050.17 1805
8 GB0.20 21230.20 21230.20 21230.20 2123
10 GB0.25 26540.25 26540.25 26540.25 2654
12 GB0.30 31850.30 31850.30 31850.30 3185
14 GB0.35 37160.35 37160.35 37160.35 3716
16 GB0.40 42470.40 42470.40 42470.40 4247
18 GB0.45 47780.45 47780.45 47780.45 4778
20 GB0.50 53090.50 53090.50 53090.50 5309
22 GB0.55 58390.55 58390.55 58390.55 5839
24 GB0.60 63700.60 63700.60 63700.60 6370
26 GB0.65 69010.65 69010.65 69010.65 6901
27 GB0.67 71140.67 71140.67 71140.67 7114
28 GB0.70 74320.70 74320.70 74320.70 7432
29 GB0.72 76440.72 76440.72 76440.72 7644
30 GB0.75 79630.75 79630.75 79630.75 7963
39 GB0.97102990.97102990.97102990.9710299
40 GB1.00106181.00106181.00106181.0010618
79 GB1.00106181.97209171.97209171.9720917
80 GB1.00106182.00212362.00212362.0021236
119 GB1.00106182.00212362.97315352.9731535
120 GB1.00106182.00212363.00318543.0031854
159 GB1.00106182.00212363.00318543.9742153
160 GB1.00106182.00212363.00318544.0042472
512 GB1.00106182.00212363.00318544.0042472
* CPW values are approximate.

Notes

  • Currently, a single IBM i VM supports a maximum of four CPU Cores (approximately 42,472 CPW).
  • If you change Entitled capacity for an active Power VM, it will display updated values but those values are not applied to the VM until it’s completely shut down, and then started again.

For Power VMs, set Entitled capacity by changing the amount of RAM and the number of CPUs.

The table below was calculated with the following formulas:

  • EC=MIN(vcpu_count,FLOOR(MAX(gb_ram/40,0.05),0.01))
  • vcpu_limit=MIN(ROUNDUP(EC*20,0),16)

Notes

  • This table provides some common RAM and CPU core combinations for Entitled capacity. You can choose other values for both RAM and CPUs—the updated Entitled capacity value displays in the Skytap interface.
  • The Entitled Capacity values in the table below are guaranteed when the corresponding RAM and CPUs are configured for the VM.
CPU Cores
RAM 5 6 7 8 9 10 12 14 16
9 GB0.22 --- --- --- --- --- --- --- ---
10 GB0.25 --- --- --- --- --- --- --- ---
11 GB0.270.27 --- --- --- --- --- --- ---
12 GB0.300.30 --- --- --- --- --- --- ---
13 GB0.320.320.32 --- --- --- --- --- ---
14 GB0.350.350.35 --- --- --- --- --- ---
15 GB0.370.370.370.37 --- --- --- --- ---
16 GB0.400.400.400.40 --- --- --- --- ---
17 GB0.420.420.420.42 --- --- --- --- ---
18 GB0.450.450.450.450.45 --- --- --- ---
20 GB0.500.500.500.500.50 0.50 --- --- ---
22 GB0.550.550.550.550.55 0.55 --- --- ---
24 GB0.600.600.600.600.60 0.60 0.60 --- ---
26 GB0.650.650.650.650.65 0.65 0.65 --- ---
27 GB0.670.670.670.670.67 0.67 0.67 0.67 ---
28 GB0.700.700.700.700.70 0.70 0.70 0.70 ---
29 GB0.720.720.720.720.72 0.72 0.72 0.72 ---
30 GB0.750.750.750.750.75 0.75 0.75 0.75 ---
40 GB1.001.001.001.001.00 1.00 1.00 1.00 1.00
80 GB2.002.002.002.002.00 2.00 2.00 2.00 2.00
120 GB3.003.003.003.003.00 3.00 3.00 3.00 3.00
160 GB4.004.004.004.004.00 4.00 4.00 4.00 4.00
200 GB5.005.005.005.005.00 5.00 5.00 5.00 5.00
240 GB5.006.006.006.006.00 6.00 6.00 6.00 6.00
280 GB5.006.007.007.007.00 7.00 7.00 7.00 7.00
320 GB5.006.007.008.008.00 8.00 8.00 8.00 8.00
360 GB5.006.007.008.009.00 9.00 9.00 9.00 9.00
400 GB5.006.007.008.009.0010.0010.0010.0010.00
440 GB5.006.007.008.009.0010.0011.0011.0011.00
480 GB5.006.007.008.009.0010.0012.0012.0012.00
512 GB5.006.007.008.009.0010.0012.0012.8012.80

Existing active Power VMs will display calculated Entitled Capacity values but those values are not applied to the VM until it’s completely shut down, and then started again.