Справочник Пользователя для IBM Flex System V7000 Expansion Enclosure 4939H29
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4939H29
Chapter 2. Introduction to IBM Flex System V7000 Storage Node
75
Draft Document for Review January 29, 2013 12:52 pm
8068ch02-HW Intro.fm
Synchronous Remote Copy ensures that updates are committed at both the primary and the
secondary before the application considers the updates complete; therefore, the secondary is
fully up to date if it is needed in a failover. However, the application is fully exposed to the
latency and bandwidth limitations of the communication link to the secondary. In a truly
remote situation, this extra latency can have a significant adverse effect on application
performance.
secondary before the application considers the updates complete; therefore, the secondary is
fully up to date if it is needed in a failover. However, the application is fully exposed to the
latency and bandwidth limitations of the communication link to the secondary. In a truly
remote situation, this extra latency can have a significant adverse effect on application
performance.
Special configuration guidelines exist for SAN fabrics that are used for data replication. It is
necessary to consider the distance and available bandwidth total network links to determine
the appropriate method to use. See 9.3, “Remote Copy” on page 380 for details on planning,
configuring and using Remote Copy for replication functions.
necessary to consider the distance and available bandwidth total network links to determine
the appropriate method to use. See 9.3, “Remote Copy” on page 380 for details on planning,
configuring and using Remote Copy for replication functions.
With the Global Mirror method there is a design option that assists with low bandwidth for
theIBM Flex System V7000 Storage Node and the other IBM virtual storage systems that
aremirroring to it running 6.4.1 code level. This option uses change volumes associated with
the primary and secondary volumes. These volumes are used to record changes to the
remote copy volume, the FlashCopy relationship that exists between the secondary volume
and the change volume, and between the primary volume and the change volume. This
function is called Global Mirror cycling mode. Figure 2-20 shows an example of this function
where you can see the relationship between volumes and change volumes.
theIBM Flex System V7000 Storage Node and the other IBM virtual storage systems that
aremirroring to it running 6.4.1 code level. This option uses change volumes associated with
the primary and secondary volumes. These volumes are used to record changes to the
remote copy volume, the FlashCopy relationship that exists between the secondary volume
and the change volume, and between the primary volume and the change volume. This
function is called Global Mirror cycling mode. Figure 2-20 shows an example of this function
where you can see the relationship between volumes and change volumes.
Figure 2-20 Global Mirror with change volumes
In asynchronous Remote Copy, the application acknowledges that the write is complete
before the write is committed at the secondary. Hence, on a failover, certain updates (data)
might be missing at the secondary. The application must have an external mechanism for
recovering the missing updates, if possible. This mechanism can involve user intervention.
Recovery on the secondary site involves starting the application on this recent “backup” and
then rolling forward or backward to the most recent commit point.
before the write is committed at the secondary. Hence, on a failover, certain updates (data)
might be missing at the secondary. The application must have an external mechanism for
recovering the missing updates, if possible. This mechanism can involve user intervention.
Recovery on the secondary site involves starting the application on this recent “backup” and
then rolling forward or backward to the most recent commit point.
2.6.5 Copy Services configuration limits
In Table 2-8 on page 76, we describe the Copy Services configuration limits. For the most
up-to-date list of these limits, see the following website:
up-to-date list of these limits, see the following website:
Note: Though this feature was added in the 6.3 code level only 6.4.1code level is
supported to mirror to the IBM Flex System V7000 Storage Node.
supported to mirror to the IBM Flex System V7000 Storage Node.