Home > Storage > PowerStore > Databases and Data Analytics > Dell PowerStore: Oracle Best Practices > Server FC HBA driver settings: timeouts and queue depth
Queue depth is the number of disk transactions that are in flight between an initiator (HBA port on a Linux server) and a target (port on a PowerStore appliance). The initiators are one or more FC or iSCSI ports on the host server which are paired with corresponding target ports of the same protocol type on PowerStore. Any given target port can be paired with multiple initiator ports. To prevent target ports from becoming flooded, the initiator queue depth throttles the number of transactions that any given initiator can send to a target port from a host. When flooding happens, the transactions are queued, resulting in higher latency, and degraded performance for the affected workloads.
The default queue depth value of 32 might be adequate for Oracle applications, but other values might work too. These values should be determined as directed in Test the I/O system before implementation.
Often, changing the default queue depth is not necessary. However, changing the queue depth might improve performance in specific use cases. These changes should only be made, tested, and evaluated in a nonproduction environment before being moved to production.
For example, if a storage array is connected to a few Linux servers with large-block, sequential-read application workloads, increasing the queue depth might be beneficial. However, if the storage has many hosts competing for a few target ports, increasing the queue depth on a few hosts might overdrive the target ports. This result might negatively impact the performance of all connected hosts.
Increasing the queue depth can sometimes increase performance for specific workloads. If the queue depth is set too high, there is an increased risk of overdriving the target ports on PowerStore. Generally, if transactions are queued and performance is impacted, try increasing the queue depth. If this change results in saturation of the target ports, increase the number of front-end target ports on PowerStore. This action to spread out I/O can be an effective remediation.