Dell PowerVault ME5 Series Administrator's Guide

Viewing I/O workload activity

The PowerVault Manager provides the I/O workload graph to help you configure the target SSD size to get the best performance for your workload. This graph presents a heat map of system activity.

The I/O workload graph shows the relationship between the workload and the amount of storage capacity used. This data reveals how much capacity is frequently accessed over time ("hot"). Under most workloads, the graph is a good indicator of data that the tiering algorithm would have put on SSDs if sufficient SSD capacity existed.

You can use this information to determine how system performance can benefit from implementing a tier of fast SSDs, instead of slower spinning disks for some or all of that capacity. Users often see the greatest performance benefits when the SSD tier is sized to handle 80% or more of the I/O workload.

Calculations are based on user-specified settings and up to eight days of usage data captured by the system.

Access the I/O Workload graph from the Dashboard:

1. Select the Capacity panel slide-over.
2. In the pool detail area for the appropriate pool, select View I/O Workload.

You can set the following options

• Values—Select whether to base the calculations on the peak values saved in the usage data or the average values. For calculations, the pool is divided into equal "bins" of LBAs. Each sample contains readings for all bins. Multiple samples are taken per day. To calculate average, the sum of the readings of a bin are divided by the number of samples. To calculate peak, the largest bin value from the collection of samples is taken. This process leaves one value for each bin, whether average or peak is selected. From there, workload calculations are made using the bin numbers as input.
• Show—Select whether to limit the data used for calculations to read I/Os only, write I/Os only, or the combined total of read and write I/Os
• Workload—Select from one to three workload calculations to display. The default calculations are based on low, mid, and high percentages of capacity: 50%, 80%, and 100%. In place of 50%, you can enter a custom percentage, which must be a whole number.