Describing different columns in a Static Service Pool Wizard
Static Service Pool (SSP) resource percentages provided in the Cloudera Manager Wizard are used as inputs to calculate internal control values such as cpu.shares, cpu.weight, blkio.weight, and io.weight. These values are not expressed as percentages in the system but as raw numbers used by the Linux cgroups subsystem to allocate resources relatively among Runtime services.
How Weights Are Calculated
The following formulas are used to compute actual values based on percentages input in the wizard:
| Resource Type | Formula | Minimum value |
|---|---|---|
| cpu.shares |
max (20, percentage * 20) |
20 |
| cpu.weight |
max(2, percentage * 2) |
2 |
| blkio.weight |
max(100, percentage * 10) |
100 |
| io.weight |
max(20, percentage * 2) |
20 |
Why do actual percentages on hosts differ?
The percentages visible in the Resource Usage tables, such as for
io.weight, are relative values derived from actual
weight * number of hosts used by each role group.
| Role Group | Hosts | io.weight (Value) | Subtotal = Hosts × Value | % of Total |
|---|---|---|---|---|
|
Impala Daemon |
3 |
100 |
300 |
300 / 740 = 40.5% |
|
YARN NodeManager |
3 |
80 |
240 |
240 / 740 = 32.4% |
|
HDFS DataNode |
3 |
20 |
60 |
60 / 740 = 8.1% |
|
Other Services such as Solr and HBase |
— |
— |
140 |
140 / 740 = 18.9% |
- Number of hosts per service
- Actual calculated value per host
- Presence of other Runtime services such as Solr, Kudu, and HBase which also receive minimum weights even if not assigned in the wizard
