Performance reporting for Logical and Physical Disks
Modern disk storage systems often map many LUN or logical volumes to other logical constructs that are referred to as extent pools or disk groups. The extent pools are composed of extents which are formatted chunks of space spread across many disks or RAID groups as shown in the picture below:
In these types of implementations the data for each LUN or logical volume is typically spread over all physical disks in the RAID array group(s) associated with the extent pools. Each array group has multiple physical disks, e.g. 8 or 16 or more. This means that a single LUN or logical disk will not cause a single physical disk to become very busy. But because physical disks can be very large, 300 Gbyte or even more, very many volumes will be mapped to one extent group. The resulting I/O density for the underlying physical disks may cause problems, especially with bad cache locality (data bases) or with high write data rates (batch workloads).
In order to avoid such performance problems it is very important to balance the workload equally over all the array groups in a disk system. Without this balance, you will not be able to exploit all the potential that the hardware offers, and performance bottlenecks may occur.
IntelliMagic Vision provides insight into the relationships between the physical and logical resources as well as the necessary performance measurement so that users can understand imbalances between the Extent Pools and supporting RAID groups.
