Overview
of boundaries and limits
This article contains information to help you understand
the tested performance and capacity limits of SharePoint Server 2010, and
offers guidelines for how limits relate to acceptable performance. Use the
information in this article to determine whether your planned deployment falls
within acceptable performance and capacity limits, and to appropriately
configure limits in your environment.
The test results and guidelines provided in this article
apply to a single SharePoint Server 2010 farm. Adding servers to the
installation might not increase the capacity limits of the objects that are
listed in the tables in the Limits and boundaries section later in this topic.
On the other hand, adding server computers increases the throughput of a server
farm, which might be necessary to achieve acceptable performance with many
objects. In some cases, the requirements for high numbers of objects in a
solution might require more servers in the farm.
Note that there are many factors that can affect
performance in a given environment, and each of these factors can affect
performance in different areas. Some of the test results and recommendations in
this article might be related to features or user operations that do not exist
in your environment, and therefore do not apply to your solution. Only thorough
testing can give you exact data related to your own environment.
Boundaries,
thresholds and supported limits
In SharePoint Server 2010, there are certain limits that
are by design and cannot be exceeded, and other limits that are set to default
values that may be changed by the farm administrator. There are also certain
limits that are not represented by a configurable value, such as the number of
site collections per Web application.
• Boundaries are absolute limits that cannot be exceeded
by design. It is important to understand these limits to ensure that you do not
make incorrect assumptions when you design your farm.
An example of a boundary is the 2 GB document size
limit; you cannot configure SharePoint Server to store documents that are
larger than 2 GB. This is a built-in absolute value, and cannot be exceeded by
design.
• Thresholds are those that have a default value that
cannot be exceeded unless the value is modified. Thresholds can, in certain
circumstances, be exceeded to accommodate variances in your farm design, but it
is important to understand that doing this may affect the performance of the
farm in addition to the effective value of other limits.
The default value of certain thresholds can only be
exceeded up to an absolute maximum value. A good example is the document size
limit. By default, the default document size threshold is set to 50MB, but can
be changed to support the maximum boundary of 2GB.
• Supported limits define the tested value for a given
parameter. The default values for these limits were defined by testing, and
represent the known limitations of the product. Exceeding supported limits may
cause unexpected results, significant decrease in performance, or other harmful
effects.
Some supported limits are configurable parameters that
are set by default to the recommended value, while other supported limits
relate to parameters that are not represented by a configurable value.
An example of a supported limit is the number of site collections
per Web application. The supported limit is 250,000, which is the largest
number of site collections per Web application that met performance benchmarks
during testing.
It is important to be aware that many of the limit
values that are provided in this document represent a point in a curve that
describes an increasing resource load and concomitant decrease in performance
as the value increases. Therefore, exceeding certain limits, such as the number
of site collections per Web application, may only result in a fractional
decrease in farm performance. However, in most cases, operating at or near an
established limit is not a best practice, as acceptable performance and
reliability targets are best achieved when a farm’s design provides for a reasonable
balance of limits values.
Thresholds and supported limits guidelines are
determined by performance. In other words, you can exceed the default values of
the limits, but as you increase the limit value, farm performance and the
effective value of other limits may be affected. Many limits in SharePoint
Server can be changed, but it is important to understand how changing a given
limit affects other parts of the farm.
How
limits are established
In SharePoint Server 2010, thresholds and supported
limits are established through testing and observation of farm behavior under
increasing loads up to the point where farm services and operations reach their
effective operational limits. Some farm services and components can support a
higher load than others so that in some cases you must assign a limit value
based on an average of several factors.
For example, observations of farm behavior under load
when site collections are added indicate that certain features exhibit
unacceptably high latency while other features are still operating within
acceptable parameters. Therefore, the maximum value assigned to the number of
site collections is not absolute, but is calculated based on an expected set of
usage characteristics in which overall farm performance would be acceptable at
the given limit under most circumstances.
Obviously, if some services are operating under
parameters that are higher than those used for limits testing, the maximum
effective limits of other services will be reduced. It is therefore important to
execute rigorous capacity management and scale testing exercises for specific
deployments in order to establish effective limits for that environment.
The
Equalizer Metaphor
You can consider thresholds and supported limits as
sliders on a graphic equalizer, with each limit representing a certain
frequency. In this metaphor, increasing the value of one limit may decrease the
effective value of one or more other limits.
Imagine that one slider represents the maximum number of
documents per library, a supported limit with a maximum tested value of around
30 million. However, this value depends on another slider, which represents the
maximum size of documents in the farm, a threshold with a default value of 50
MB.
If you change the maximum size of documents to 1 GB to
accommodate videos or other large objects, the number of documents your library
can serve to users efficiently is reduced accordingly. For example, a given
farm’s hardware configuration and topology may support 1 million documents up
to 50 MB. However, the same farm with the same number of documents cannot meet
the same latency and throughput targets if the farm is serving a larger average
document size because the file size limit was set to 1 GB.
The degree to which the maximum number of documents is
reduced in this example is difficult to predict and is based on the number of
large files in the library, the volume of data that they contain, the farm’s
usage characteristics, and the availability of hardware resources.
Use these
guidelines to review your overall solution plans. If your solution plans exceed
the recommended guidelines for one or more objects, take one or more of the
following actions:
•
Evaluate the solution to ensure that compensations are made in other areas.
• Flag
these areas for testing and monitoring as you build your deployment.
•
Redesign or partition the solution to ensure that you do not exceed capacity
guidelines.
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