IBM Flex System V7000 Expansion Enclosure 4939H29 ユーザーズマニュアル

Chapter 2. Introduction to IBM Flex System V7000 Storage Node 

Draft Document for Review January 29, 2013 12:52 pm

With the IBM Flex System V7000 Storage Node there is a capability to create a volume as a 
compressed volume type. With this type of volume storage capacity needs can be lowered by 
as much as half. IBM Flex System V7000 Storage Node RTC function is based off of the 
same proven Random-Access Compression Engine (RACE) as the IBM RTC Appliances. 

With compression, storage growth can be curbed and need for additional storage purchases 
can be delayed and spread out over greater periods of time. RTC dynamically works with 
active workloads now compresses the data while it is being processed the first time.

To implement RTC the volume must be created with compressed type selected. You cannot 
convert a volume from uncompressed to compressed after creation. However, a compressed 
volume can be a target of a volume mirror allowing the copying of the uncompressed volume 
to a compressed copy. 

The RTC is a feature that is licensed on an enclosure basis for the IBM Flex System V7000 
Storage Node. 

RTC resource needs should be considered when planning for the use of compression. 
Resource requirements must come from someplace. Understanding the best balance of 
performance and compression is an important factor to consider when designing a mixed 
compressed environment. 

RTC can be purchased to run on one control enclosure (IO Group) of a cluster and not for 
another allowing for shared environments to exist depending on need and providing 
environments that meet the needs.

To gain insight of the what should be expected a tool has been created which can be used to 
gather details and provide input on the workload type and pattern to show its level of 
compressibility. A tool called the Comprestimator can be used to analyze data gathered.

For more information on the usage and capabilities of this feature see Real-time Compression 
in SAN Volume Controller and Storwize V7000, REDP-4859 at the following url:

iSCSI is an alternative means of attaching hosts to the IBM Flex System V7000 Storage 
Node. All communications with external back-end storage subsystems, or other IBM virtual 
storage systems must be done through a Fibre Channel or FCOE connection.

The iSCSI function is a 

 that is provided by the IBM Flex System V7000 

Storage Node code, not hardware.

In the simplest terms, iSCSI allows the transport of SCSI commands and data over a TCP/IP 
network, based on IP routers and Ethernet switches. iSCSI is a block-level protocol that 
encapsulates SCSI commands into TCP/IP packets and uses an existing IP network, instead 
of requiring expensive FC HBAs and a SAN fabric infrastructure.

A pure SCSI architecture is based on the client/server model. A client (for example, server or 
workstation) initiates read or write requests for data from a target server (for example, a data 
storage system).