Storage Thresholds
Standard storage thresholds are listed below.
Online Response-oriented System | Batch Throughput-oriented System | |
|---|---|---|
LogicalVolume Response | 30 ms or less | - |
RAIDGroup Busy Rate | 60% or less | 80% or less |
CM Busy Rate | 80% or less | 90% or less |
For a response-oriented system such as for online applications, implementing LogicalVolume responses within 30 ms is a standard for stress-free storage operation. To implement responses within 30 ms, suppress the RAIDGroup busy rate to 60% or less and the CM busy rate to 80% or less.
In a throughput-oriented system such as for batch applications, LogicalVolume responses are extended to a few milliseconds because sequential access increases the cache hit ratios. However, the cache hit ratios are greatly affected by application access and the values change a great deal. As a result, responses may vary from a few milliseconds to 50 ms or more. Thus, for batch applications, there is no standard threshold for LogicalVolume responses.
To improve throughputs for batch applications, users must optimize the use of storage resources. Note, however, that performance may deteriorate rapidly if the above threshold is exceeded. For this reason, make it a standard to suppress the RAIDGroup busy rate to 80% or less and the CM busy rate to 90% or less.
During hours in which advanced copy is processing, advanced copy processing itself increases the CM busy rate.
For this case, set thresholds in consideration of execution of advanced copy.
Thresholds of Switch Ports
The threshold and lower limit value vary depending on the type of applicable switch (1 Gbps, 2 Gbps, etc). When the switch type is 1 Gbps, the maximum value (100% use rate) is 100 MB/s. When the switch type is 2 Gbps, the maximum value is 200 MB/s. For the threshold, specify the allowable utilization (%) corresponding to the maximum value.
For instance, when 90% is specified for the threshold of a 2 Gbps type switch, the threshold of the throughput is:
200 MB/s x 90% = 180 MB/s (total of reception and transmission)
An alarm is given when the throughput reaches 180 MB/s.
Switch port threshold monitoring is effective when there is a difference in the numbers of paths between the server and storage.
