Quality of Service policies enable you to define quality of service per view. Within quality of service policies, you can set maximum limits on read and write bandwidth and IOPS per view. Those limits can be:
Static limits for the view. You can set these limits without provisioning a quota for the view path.
Based on used capacity. You can set maximum limits on the bandwidth and IOPS for reads and writes to the view, per amount of used logical capacity. Logical capacity is the amount of data written, before data reduction.
This mode requires a quota to be provisioned on the view path. If you attach a QoS policy that uses this mode to a view that has no quota, VMS creates a quota on the view path.
Based on the amount of logical capacity provisioned by a quota on the view path. The relevant quota limit is the soft limit defined in the quota.
The quota on the view path itself is the only quota that affects the limits.
QoS limits take both data workload and metadata requests into account, as follows:
- The size of a single IO for the purpose of a QoS limit is 1MB. In other words, the number of IOs per request is obtained by dividing the request size by 1MB.
- A mutating metadata request (such as create, delete, rename, setattr) is counted as one write IO. Non-mutating metadata requests (such as getattr, lookup, list) are counted as one read IO for each. The size of a metadata request is taken to be 4KB.
QoS policies are supported for NFSv3, NFSv4.1 and SMB.