Setting Domain Restrictions
When new domains are created, the default domain setting is Unrestricted, meaning that there are no limits on throughput or number of inputs/outputs per second (I/Ops) for that domain. In situations where the available I/Ops and throughput resources are sufficient to meet the demands of the various concurrently active domains, there is no need to change the default setting.
Guidelines for Domain Restrictions
When available resources are over subscribed or multiple domains are competing for throughput priority, you can change the domain settings to enable the Quality of Service (QOS) feature to restrict I/Ops and throughput resources. Restricting throughput for less critical domains allows critical domains to be able to access storage whenever necessary; non-critical domains may be primarily active during periods when they do not impact other critical domains.
Limiting I/Ops is useful for domains that issue many small data transfer operations— commonly referred to as transaction-oriented domains. Limiting throughput is useful for domains that issue few large data transfer operations, commonly referred to as throughput-based domains. Some common examples of the extreme of these cases are database application domains which are transactions-oriented and back up application domains which are throughput-oriented.
Viewing Domain Performance
You can view performance of the domain using the Performance tool in the SANcentral interface. The restrictions (if any) that you have placed on the domain will display in the KB/s and I/Os fields when a domain is selected. Also you can select the DataCore Domain Object and various counters in Windows Performance Monitor. Refer to Windows Performance Monitor for more information. If you have applied domain restrictions (QOS) and the Domain Performance tool shows that the domain is not achieving the restrictions you have set, it may be because:
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Application servers in the domain are not able to achieve the settings.
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Storage servers themselves are not capable of arriving at the restrictions you have set.
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The set of applications themselves are not creating enough I/O to reach the restrictions you have set.
To restrict the domain competing for total available throughput:
The Settings dialog box, where you can change cache size and restrict domain throughput, can be found in the SANcentral interface, by selecting Settings from the Tools menu. For information on changing cache size, refer to Setting Cache Size.
In the Settings dialog box, select the domain (left pane) and choose Restricted in the Domain Restriction area on the right. Enter the maximum aggregate throughput and aggregate I/Os per second for the selected domain— this sets the Quality of Service (QOS). Refer to the table below for more information.
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Display with Domain Highlighted |
Description |
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Unrestricted |
This mode of operation imposes no limitation on any domain for number of I/Os per second (I/Ops) or throughput resources. This is usually the case where total available storage server resources are more than sufficient to meet performance needs of the various domains. The Unrestricted class of service is targeted for use by applications requiring the lowest possible I/O latency. A domain which is Unrestricted has no QOS feature applied, i.e., no artificial limitations are placed on that domain. This is the default. |
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Restricted |
This mode of operation imposes limitations on a domain: either I/Ops, Bandwidth (throughput) or both. Imposing resource consumption limits makes it possible to prioritize the competing domains access to storage resources. In this way it is possible to ensure that critical domains are not impacted by storage resource competition. The Restricted class of service is targeted for use by applications that will include members of a domain who are not sensitive to I/Ops and throughput constraints. Examples include nightly backups and Asynchronous IP Mirroring (AIM). |
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Max bandwidth in MB/sec |
This setting restricts the amount of data being transferred in MB per second. Customize this setting to restrict a domain that is running throughput-bound applications (very large data transfers). |
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Max number of IOs/sec |
This setting restricts the number of reads/writes per second. Customize this setting to restrict a domain that is running I/O-bound applications (heavy traffic of small data transfers of less than 8 KB). |
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Cumulative Performance |
You can reset the counters of total I/O and bandwidth (throughput) used in the Cumulative field of the Performance tool in the SANcentral interface. For information on viewing domain performance, refer to the section on Viewing Domain Performance (above). |
Related Topics:
Changing Domain Properties