82 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
3.19.3  Storwize V7000
The Storwize V7000 clustered system is scalable up to eight nodes. Its performance grows 
nearly linearly when more nodes are added until it becomes limited by other components in 
the storage infrastructure. Although virtualization with the Storwize V7000 provides a great 
deal of flexibility, it does not abolish the necessity to have a SAN and back-end storage 
subsystems that can deliver the performance that you want. 
Essentially, Storwize V7000 performance improvements are gained by using in parallel as 
many physical disks as possible, which creates a greater level of concurrent I/O to the 
back-end storage without overloading a single disk or array. 
Assuming that no bottlenecks exist in the SAN or on the disk subsystem, you must follow 
specific guidelines when you perform the following tasks:
/SM590000Creating a storage pool
/SM590000Creating volumes
/SM590000Connecting to or configuring hosts that use storage presented by a Storwize V7000 
clustered system
For more information about performance and preferred practices for the Storwize V7000, see 
IBM System Storage SAN Volume Controller and Storwize V7000 Best Practices and 
Performance Guidelines, SG24-7521.
3.19.4  IBM Real-time Compression
IBM Rational® Team Concert® technology in storage systems is based on the Random 
Access Compression Engine (RACE) technology. It is implemented in IBM Storwize V7000 
and the IBM Storwize family, IBM FlashSystem V840 systems, IBM FlashSystem V9000 
systems, and IBM XIV (IBM Spectrum Accelerate™). This technology can play a key role in 
storage capacity savings and investment protection. 
Although the technology is easy to implement and manage, it is helpful to understand the 
basics of internal processes and I/O workflow to ensure a successful implementation of any 
storage solution. 
Consider the following suggestions:
/SM590000Best results can be achieved if the data compression ratio stays at 25% or more. Volumes 
can be scanned with the built-in Comprestimator utility to support decision if IBM Rational 
Team Concert™ is a good choice for the specific volume.
/SM590000More concurrency within the workload gives a better result than single-threaded 
sequential I/O streams.
/SM590000I/O is de-staged to RACE from the upper cache in 64 KiB pieces. The best results are 
achieved if the host I/O size does not exceed this size.
/SM590000Volumes that are used for only one purpose usually have the same work patterns. Mixing 
database, virtualization, and general-purpose data within the same volume might make 
the workload inconsistent. These workloads might have no stable I/O size and no specific 
work pattern, and a below-average compression ratio, which makes these volumes difficult 
to investigate during performance degradation. Real-time Compression development 
advises against mixing data types within the same volume whenever possible.
/SM590000It is best to not recompress pre-compressed data. Volumes with compressed data should 
stay as uncompressed volumes.