Oracle Performance Tuning Stripe width

Whether one or more disks respond to a logical I/O, we all require that I/O be processed at once. Therefore, on the basis of determining the band depth, we need to ensure the stripe bandwidth degree >= I/O request size/stripe depth.

In addition, considering the future expansion of the system capacity, we also need to plan a good stripe width.

Most LVM today Support Online dynamic addition of disks. That is, when disk capacity is low, we can add new disks to a logical volume that is already in use at any time. In this way, we can simply put all the disks into a volume when we set up a logical volume.

However, some LVM may not yet support dynamic disk addition. At this point we need to consider the impact of future capacity expansion on I/O equalization.

Because your new disk cannot be added to the original volume, you need to make a new volume. However, the general expansion of the capacity and the original capacity is relatively small, if the original volume bandwidth ratio is large, the new increase in the stripe width of the volume can not reach its size, so that the new, old volume between the I/O imbalance.

For example, the initial configuration of a system is a single logical volume consisting of 64 disks, each with a disk size of 16G. The total size of the disk is 1T. As the data in the database grows, 80G of space needs to be added. We have added a new 5 16G disks into a logical volume.

This results in an I/O imbalance on two volumes. In order to avoid this situation. We can configure the original disk to be a 8 logical volume with 8 disks per stripe, which can also be added to a new volume of 8 disks when the new disk is added. However, you must ensure that the stripe width of 8 disks supports the system's I/O throughput per second.

If your stripe width is set to a smaller size, you need to estimate the I/O load of your individual database files and deploy them to different volumes to share the I/O load, depending on the amount of load.

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