From the vantage point of business solutions, it is not unusual to consider
storage as just a bunch of disks, acquired simply to fulfill the storage
needs of the real business. But when demands on business processes drive
increased storage needs, it becomes clear that the key cost driver is
not the procurement of the storage hardware, but rather its management.
Administrators need to make sure that all systems of a mySAP landscape
have sufficient storage, and that added disks do not become hotspots that
can impair business-critical I/O throughput.
Monitoring and managing storage within
each individual system of a mySAP landscape may become a challenge. With
the ever-increasing need for continuous business availability, many SAP
customers are finding they need storage solutions that go beyond additional
Happily, todays state-of-the-art
storage systems are more than just another container for business
data. This article will introduce you to the key technology now available
for enhanced management of storage in complex system environments
environments familiar to almost every SAP customer as well as some
of the business-critical features to look out for as you evaluate storage
But Dont I Already Have a Storage System?
Storage systems go beyond the traditional approach of monitoring storage
locally and managing it within each individual SAP system (i.e., your
BW solution on one server, your CRM solution on another). For the purposes
of this discussion, a storage system is a dedicated computer
with special-purpose disk storage management functions, specifically designed
to consolidate the storage demands of multiple hosts. These functions
- Reliability and Availability: All components of the storage
systems are redundant, so that in case of a malfunction, the remaining
component can take over the work. The data on the physical disks is
RAID protected. This means that the storage systems always keep redundant
data in order to reconstruct the data in case of a failed disk.
- Scalability: Should storage needs grow, the capacity of the
storage systems can easily be expanded without impact on operation.
- Performance: The storage systems capability to stripe
data across multiple physical disks together with memory-cached
I/O, and special-purpose CPUs for disk-to-cache as well as cache-to-host
interfaces offer business-critical high-I/O throughput.
The good news is that whether you are a
large enterprise that spends a large part of its IT budget for storage
or a smaller enterprise with more limited needs, today a variety of vendors
offer this technology at reasonable prices. Nearly all storage manufacturers
have started initiatives to provide tools capable of managing multi-manufacturer
storage landscapes. And since these tools will protect your storage investments,
why wait to reap all the benefits that a storage system provides?
Key Features of Storage-Based Solutions for mySAP Landscapes
In collaboration with our partners from storage and database manufacturers,
SAP makes every effort to offer solutions that optimize operation and
infrastructure of mySAP landscapes.
Storage systems include fast copy functions
available for copies within (local) and between (remote) storage systems.
These copies are executed in the storage systems themselves without reducing
a hosts CPU power. These capabilities, in combination with special
database functions, allowed for the development of the split mirror
Split Mirror Solution
This is a key building block for storage solutions and provides a
consistent copy of a database without any impact to operation. For this,
the database systems offer functions that temporarily halt WRITE operations
in a controlled manner (SUSPEND/RESUME) and log the status of transactions
as complete or open in the database
While the database is in SUSPEND mode,
all volumes that contain the database will be copied on the storage level.
Of course, each implementation depends on the used database and storage
system. However, the achieved copy (backup) can be used for a point-in-time
recovery, and in combination with the recent DB-logs for a forward recovery.
If you wish to create consistent landscape
copies in this way, you must ensure that the SUSPEND commands in all
the database systems you use are coordinated.
Solutions based on the split mirror solution
- Non-impact backup
Business operation is merely throttled, while the copy on the storage
- Fast recovery
Since the most recent backup is kept in the storage system, it can be
used immediately for a recovery.
- Landscape cloning
The point-in-time copy of a mySAP landscape can be used as an emergency
system landscape, for read-only purposes or for testing system upgrades.
There are additional approaches that storage-based
solutions can use to help further maximize your storage system: consistency
groups, a concept that provides a split mirror solution without database
participation, and remote copy capabilities to provide a
standby landscape for high data availability in case of a disaster.
Some storage systems, meanwhile, embrace the concept of consistency
groups to suspend READ/WRITE operations. A consistency group consists
of disks that are distributed over one or more storage systems. The idea
behind this concept is to store the data for all the systems in a mySAP
landscape in a consistency group, then use this group to create a consistent
landscape copy while WRITE operations are suspended.
Unfortunately, database manufacturers do
not currently recognize copies created in this way as backups.
However, these copies can certainly be used to create a landscape clone.
This new point-in-time copy of your mySAP landscape can then be used as
an emergency system landscape for read-only purposes or for testing system
Remote Copy Capabilities
Even a clone of your mySAP landscape may sometimes not fulfill your
availability requirements. To be prepared for a major disaster
like the loss of the storage system or the entire computing center
the data of a mySAP landscape must be copied to a secondary storage system
located either in the same or a remote computing center. This can be achieved
by the storage systems remote copy capability.
An Example of Storage Systems for a mySAP Landscape
Suppose you have a mySAP landscape composed of three servers devoted
to R/3, SAP CRM, and SAP BW, and you are looking to simplify your storage
management processes. When adding a storage system to the landscape, you
could place primary and secondary storage systems on either a single computing
center, or on two separate computing centers as in Figure 1. Choosing
the latter setup provides maximum protection against both the loss of
the primary storage system and the loss of the computing center it operates
||A Sample SAP Landscape with a Storage System
Figure 1 depicts optimal storage layout,
non-impact backup, standby landscape, and cloned landscape
features in storage-based solutions.
In order to get the full I/O bandwidth
for all systems of the mySAP landscape, the logical volumes are not only
striped across the disks controlled by one disk adapter, but across all
disk adapters .
All data changes on the primary system
will be immediately copied via synchronous remote copy to the secondary
system . The first
mirror becomes the standby landscape copy.
A consistent backup of the landscape will
be achieved by the split mirror solution. For this, the WRITE I/Os
will be suspended on the primary side on the database level ;
in the secondary storage system, a second mirror will be created
and copied to tape .
Here youll find great benefits to
availability: since the physical copy of the backup will be processed
on the secondary storage system, the full I/O bandwidth of the primary
system is available for the productive mySAP landscape.
After the backup, a cloned landscape
can be started
on the second mirror. Since this will modify the database images, they
must be reloaded from tape in case of a recovery. To be able to provide
a fast recovery nevertheless, a third mirror should be kept either on
the primary or the secondary storage system.
Both the primary and the secondary hosts
are connected by a switched fabric to the storage systems .
The dotted lines between the primary hosts and the secondary storage system
depict that the
primary hosts can take over the data from first mirror in the secondary
storage system should the primary hosts fail. In case the entire primary
computing center is lost, the secondary hosts continue to work on the
For More Information
Although most storage systems offer advanced data distribution strategies
to avoid hotspots, SAP provides recommendations and best practices on
how to lay out the databases of a mySAP landscape on a storage system.
However, in case a customer does encounter trouble with I/O issues, SAP
offers a storage optimization service. For more information, SAP customers
can log on to http://service.sap.com/stso.
Best practices and white papers regarding
storage-based solutions are available from SAP or the storage manufacturers.
For further information on these topics, SAP customers can refer to http://service.sap.com/atg.
Schmidt joined SAP in April 1989
in development of SAPs interfaces
to database platforms. In 1997, he became
a member of the Advanced Technology Group a
department in SAPs support organization.
On selected projects, he supported customers
and the R/3 development team in optimizing
mission-critical processes and performance.
Currently, he develops, in cooperation with
manufacturers of storage subsystems, infrastructure
concepts and solutions that meet customers requirements
of system availability, ease of administration,