72 IBM Flex System V7000 Storage Node Introduction and Implementation Guide
2.6.13 Real-time Compression
With 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
more than half. IBM Flex System V7000 Storage Node Real-time Compression function is
based on the same proven Random-Access Compression Engine (RACE) as the IBM
Real-time Compression Appliances (RtCA).
With compression, storage growth can be curbed and the need for additional storage
purchases can be delayed and spread out over greater periods of time. Real-time
Compression dynamically works with active workloads now, compressing the data while it is
being processed for the first time.
To implement Real-time Compression, 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 Real-time Compression feature is licensed on an enclosure basis for IBM Flex System
V7000 Storage Node.
Real-time Compression resource needs should be considered when planning for the use of
compression. Resource requirements must be planned. Understanding the best balance of
performance and compression is an important factor to consider when designing a mixed
compressed environment.
Real-time Compression can be purchased to run on one control enclosure (I/O Group) of a
cluster and not for another, allowing for shared environments that exist depending on need
and providing environments that meet the needs.
To gain insight of what should be expected, a tool has been created that can be used to
gather details and provide input on the workload type and pattern to show its level of
compressibility. An IBM tool called the Comprestimator can be used to analyze data gathered.
For more information about the usage and capabilities of this feature, see Real-time
Compression in SAN Volume Controller and Storwize V7000, REDP-4859, at this website:
http://w3.itso.ibm.com/redpieces/abstracts/redp4859.html?Open
2.6.14 iSCSI
iSCSI is an alternative means of attaching hosts to 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
software function that is provided by 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.
Note: IBM Flex System V7000 Storage Node version 7.1.x or later supports the use of
Real-time Compression and Easy Tier together, which enables users to gain high
performance and high efficiency at the same time.
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