HP 6400/8400 HP StorageWorks Enterprise Virtual Array updating product softwar - Page 31

Counter Read Miss Data Rate Read Miss Latency Write Req/s Write Data Rate Write Latency Flush Data Rate Mirror Data Rate Prefetch Data Rate Description The rate at which data is read from physical disks because the data was not present in the array cache memory. The average time it takes to complete a read request (from initiation to information receipt) from the physical disks. The number of write requests per second completed to a virtual disk that were received from all hosts. Write requests may include transfers from a source array to this array for data replication and host data written to snapshot or snapclone volumes. The rate at which data is written to the virtual disk by all hosts and includes transfers from the source array to the destination array. This average time it takes to complete a write request (from initiation to receipt of write completion). The rate at which data is written to a physical disk for the associated virtual disk. The sum of flush counters for all virtual disks on both controllers is the rate at which data is written to the physical drives and is equal to the total host write data. Data written to the destination array is included. Host writes to snapshots and snapclones are included in the flush statistics, but data flow for internal snapshot and snapclone normalization and copy-before-write activity are not included. The rate at which data travels across the mirror port to complete read and write requests to a virtual disk. This data is not related to the physical disk mirroring for Vraid1 redundancy. Write data is always copied through the mirror port when cache mirroring is enabled for redundancy. In active/active controllers, this counter includes read data from the owning controller that must be returned to the requesting host through the proxy controller. Reported mirror traffic is always outbound from the referenced controller to the other controller. The rate at which data is read from the physical disk to cache in anticipation of subsequent reads when a sequential stream is detected. Note that a sequential data stream may be created by host I/O and other I/O activity that occurs because of a DR initial copy or DR full copy. Managing host I/O timeouts for an online upgrade The default values for host operating parameters such as LUN timeout and queue depth are typically set to values that ensure proper operation with the storage system. These values are appropriate for most storage system operations, including online firmware upgrades. In general, host LUN timeouts of 60 seconds or more are adequate to accommodate an online upgrade. In most situations it will not be necessary to alter these settings to perform an online firmware upgrade. If any host timeout values have been decreased to less than 60 seconds, it will be necessary to reset them to their original default value. The following section provide a summary of the steps and commands involved in checking and changing timeout values for each supported operating system. See the operating system documentation for more information. HP StorageWorks Enterprise Virtual Array updating product software guide (XCS 09522000) 31