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The fact that a storage device (LUN) is causing a lot of I/O waits could be caused from an intensive load or as a result of two sorts of contentions: a logical contention (e.g. imbalanced activity of the database) or a physical contention (e.g. one of the underlying physical devices is being shared with another heavy I/O consuming activity).
| Storage Contention On Device findings |
| Description | |
| What to do next | n Examine the device activity over time and database files contention. n Examine storage device statistics and contention on the Raid Group and Physical Disks. |
| Advice | n If the device is loaded by the monitored database only and by a singular entity (e.g. a file, object, or partition), consider splitting this load (e.g. separating the objects in the file, partitioning the object, etc). n To relieve inter application logical contention, check if the database's I/O activity is balanced. Spread heavy I/O consuming files across the storage devices, to avoid a situation in which few heavy files reside on the same storage device. n To relieve intra application logical contention, check whether there are additional applications using the storage device. For example, if the number of I/O requests processed by the storage device is significantly higher that the requests sent by the database, it means that the storage device is being used by an additional application. n To relieve physical contention, check whether there is significant I/O activity in the underlying shared physical disks and raid group. Another potential cause of contention are the EMC adapters (front director and disk director). If the load is imbalanced, consult with the storage administrator about relocating the information to other disks which reside on a more vacant location. n Consider storage tiering - a faster device may reduce the I/O wait time significantly. |
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