Configuring sql server - SQL Saturday, Athens Oct 2014
polyserve-sql-server-scale-out-reporting
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Scalable Shared Databases for SQL Server 2005
Achieving Linear Scalability for Scale-out Reporting using
SQL Server 2005 Enterprise Edition
Abstract: Microsoft SQL Server™ 2005 Enterprise Edition supports scale-out
reporting through scalable shared databases. Scale-out reporting enables multiple
SQL Server 2005 systems to attach a read-only copy of the same database.
When deployed using PolyServe’s Database Utility™ for SQL Server, Enterprises
reduce report completion times by up to 16x. The solution reduces storage
complexity, simplifying SQL Server scale-out for complex, off-hours reporting
workloads. The PolyServe solution enables rapid transformation of OLTP to read-
only data warehousing for scale-out and back again to OLTP—in seconds.
This proof of concept (POC) demonstrates PolyServe’s solution for scalable shared
databases. The POC consists of a 4-node PolyServe Matrix Server cluster running
PolyServe’s Database Utility for SQL Server and Microsoft SQL Server 2005
Enterprise Edition, connected to a SAN.
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Scalable Shared Databases for SQL Server 2005.....................................................1
Achieving Linear Scalability for Scale-out Reporting using SQL Server 2005 Enterprise Edition ....... 1
Introduction ...............................................................................................................2
Single System Performance Limits ..................................................................................................... 2
Data Warehousing Challenges ........................................................................................................... 3
Introducing the Scalable Shared Database................................................................3
Analysis............................................................................................................................................... 4
Another Model for Scale Out: Shared Data................................................................5
Storage Management.......................................................................................................................... 5
Concurrent Scalability—for Scale Out................................................................................................. 6
Proof of Concept Results...........................................................................................6
Data Center Use Case........................................................................................................................ 7
Configuration Overview....................................................................................................................... 8
Database Configuration Overview ...................................................................................................... 8
Performance Results........................................................................................................................... 8
Conclusions.............................................................................................................11
The Database Utility Overview ................................................................................12
The Database Utility™ for SQL Server Components ...............................................13
PolyServe’s Cluster Volume Manager .....................................................................14
Summary.................................................................................................................15
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Introduction
With rapidly growing production databases deployed on Microsoft SQL Server 2005,
the need for timely and scalable reporting operations has become a business-critical
need among Enterprises.
Today, the size of databases deployed on individual SQL Server systems is often
measured in the hundreds of Gigabytes to Terabytes. For larger databases, data
warehouse preparation is challenging and time-consuming.
Further, companies face time-constrained reporting windows where there is
effectively less time and (as the database grows) less available computing power to
complete resource-intensive reporting jobs within an off-hours reporting window.
Single System Performance Limits
When the power of SQL Server 2005 is combined with modern, industry-standard
x64 servers and Storage Area Networks (SANs), Enterprises are provided with a
robust platform for deploying mission-critical databases, at an optimal price-
performance. For single system scalability, SQL Server 2005 possesses numerous
performance and memory management advancements to exploit resource utilization
within a single system.
For Online Transaction Processing (OLTP)—where queries tend to be shorter and
less resource-intensive—a single server often provides adequate bandwidth.
However, more complex workloads—such as reporting, ad hoc queries, and data
warehouse preparation—often require more throughput than a single server can
provide. Scanning tables, sorting large amounts of data, and running multiple
reporting jobs concurrently—all against the same database—these are resource-
intensive tasks that can easily overburden a single server system. For these
workloads, the server is often the bottleneck.
Consider a business requirement to execute 8 reports against a 300GB table used
primarily for OLTP. The indexes have been optimized for OLTP. The query plans
generated for the reports are based upon full table scans. If such reporting saturates
a single server, the only way to complete the 8 reporting jobs in less time is to scale
out to several servers, running multiple reports concurrently across multiple servers.
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Data Warehousing Challenges
Data warehouses and data marts often start small and simple (with a fact table or
two and a few dimension tables). If successful, these small data warehouses may
grow across an organization over time, transforming into corporate-wide repositories
used for business intelligence and senior management decision support.
One goal behind transforming a large read-write database to a read-only data
warehouses is to offload performance-intensive reporting functions to another server.
Another overarching goal of a data warehouse is to maintain fresh data. Every
second spent on data warehouse preparation means less time spent on reporting—
and progressively less up-to-date data.
From a performance perspective, it does not take long for multiple reporting
operations to overburden servers and direct-attached storage during the off-hours
data warehouse preparation and reporting usage periods.
When faced with a fixed amount of time and fixed amount of bandwidth, the scalable
shared database is a revolutionary breakthrough.
Introducing the Scalable Shared Database
Microsoft SQL Server™ 2005 Enterprise Edition supports scale-out reporting through
Scalable Shared Databases. Scale-out reporting enables multiple SQL Server 2005
instances to attach a read-only version of the database.
The KB article focuses on use-cases for reporting and data warehouse activity.
In summary, the implementation described in the Microsoft KB article recommends
the following configuration guidelines:
• Read Only NTFS Volumes. A Scalable Database must reside in a read-only
volume or set of volumes. Note: this POC validates using Scalable Shared
Databases on the PSFS (PolyServe File System), an NTFS-compatible file
system built using Microsoft’s Installable File System (IFS) Kit.
• Private tempdb. The Scalable Database must be attached to an instance
that has private tempdb.
• SAN. The database must reside on a read-only volume configured using the
diskpart.exe utility from the database server attached to a Storage Area
Network. This POC obviates the need for this function.
• Windows Version Requirement. Scalable Shared Databases are supported
only on Microsoft Windows Server 2003 Service Pack 1 or later.
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The non-shared data approach described in the KB article documents how to
maintain an updated copy of the production database. To use this copy of the
database for scale-out reporting, a new read-only volume must be created and
managed using DISKPART.exe. To do so, a volume and its database copy must be
unmounted and remounted in read-only mode on all the reporting servers.
Conversely, the volume must then be unmounted from all the reporting servers and
re-mounted in read-write mode to refresh its contents (i.e., bring the database copy
up to date with the production database). This cycle must be repeated for each
reporting exercise. To say the least, it’s a complicated process.
This approach has been tested with scaling out to 8 nodes by Microsoft Corporation.
Analysis
The approach covered in the KB article is based on using read-only volumes
containing replicated database copies for reporting. This is a functional approach.
But, given the operational overhead, likely not entirely useful.
An essential premise behind scalable shared databases is that the production
database is large and growing and cannot be easily serviced by a single server for
reporting or ad hoc query purposes.
There are still challenges with scale out:
• Each database requires a replicate or snapshot copy to manage. This
creates storage management overhead. There is effectively more storage
and data to manage, across more logical management points—for both the
storage operator and DBA.
• Costly processing refreshes. Refreshing the replicated database affects
the production database.
• Challenging to administer free space. There will be space management
tasks for 1 large production database and its large replica.
• Challenging to maintain. Since the database is large, it would likely reside
in several volumes, each of which must be individually managed. Mounting
and unmounting volumes on each reporting server also creates
administration overhead.
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In the non-shared data approach, the volumes used for the replicated reporting
database should be dedicated exclusively to reporting, since the volumes will be
routinely unmounted and re-mounted in read-only mode. This will likely increase the
total number of volumes to manage, per cluster.
Another Model for Scale Out: Shared Data
Another deployment option for scaling out databases on SQL Server 2005 is shared
data. Through PolyServe’s Database Utility, all servers have read-write access to all
storage. This makes storage management, data warehouse preparation time, and
scale out and back for reporting, an easy operation.
To fully exploit the scale-out databases, an environment that supports scaling out to
many nodes without replication and without explicit volume creation (as read-only),
or mount/unmount operations, may be supported using the PolyServe solution.
Storage Management
Storage management is greatly simplified because all servers can “see” all storage.
There are few volumes to manage, and storage does not have to be reconfigured. In
the utility model, storage does not have to be reconfigured to be used in support of
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scalable shared databases. Once provisioned, databases can be easily moved from
server to server, in support of scale out and scale back operations.
Concurrent Scalability—for Scale Out
Through a simple script operation, all SQL Server systems may attach the database
as read-only. Reports or ad hoc queries can safely run on a server without affecting
the performance of reports or queries running on other servers.
In effect, reports are isolated to a given server. More servers can be added as
needed, running concurrently across more servers—against the same data.
Proof of Concept Results
As summarized above, SQL Server 2005 enables attaching a database in a read-
only volume to more than one server. With PolyServe, there is no manual volume
creation required. Attaching the read-only database to multiple servers can be
automated through scheduling, or performed manually through a few easy steps.
This vastly simplifies the job for the DBA. Now, instead of having to create, mount
and un-mount multiple volumes to each new server in the cluster, a simple file group
permissions operation is sufficient. Thus, the production database itself can be
scaled out (mounted by multiple servers) in support of reporting operations.
The benefits of Scalable Shared Database in the PolyServe Database Utility for SQL
Server:
• No stale data—work in near-real-time. The database can be kept up-to-date
since no copying via replication nor are snapshots required. While replication
and snapshots are both supported in the PolyServe solution, there is no need
for replication, or snapshots—unless the reporting job takes place on a
remote cluster.
• Single-touch scale-out. Since this solution is based on PolyServe’s solution
for Windows Server, the degree of scale-out is 16 servers.
• No need for operator intervention to perform complicated mount/unmount
operations
• Rapid transformation from OLTP to Scalable Shared Database for reporting
operations, and back again
o Transform from OLTP to Scalable Shared Database on 16 servers in
less than 60 seconds
o Scale back to read-write mode in less then 30 seconds
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Figure 1: Proof of Concept Main Table with 1,000,000 rows
o Reporting can begin within seconds on current data on up to 16
servers
• Volumes can be shared—and do not have to be dedicated to the scale-out
database
• Tempdb databases for all servers can reside in the same high-performance
volume as the production database
• No need to burden internal drives and other server resources. Since
operations are automated, there is less burden on each server hosting the
scale-out database.
• No “volume sprawl”. Since all pre-defined servers can share volumes in the
SAN, there are fewer volumes to create, manage, and backup.
• Single point of backup. During the reporting window, one or more nodes in
the cluster may be dedicated to backing up the production database while
reporting jobs occur in parallel.
Data Center Use Case
Most datacenters dedicate
certain hours of operation to
reporting, ad hoc queries, and
data warehouse preparation.
With PolyServe’s Utility
approach to Scalable Shared
Databases, not only is the
transformation of the same
database from OLTP to
reporting performed in a matter
of seconds, but the degree of
scalability can be up to 16
servers. With 16 servers
working on a set of reports, or
performing intensive data
warehouse preparation, the
resultant window is reduced
significantly freeing time to
perform important database
maintenance operations.
For example, consider a data
center that currently performs,
say, 50 reports each night in a
reporting window of 4 hours. With the PolyServe approach to Scalable Shared
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Figure 2: Proof of Concept Main Table
File Properties
Database, the reporting could be reduced to as little as approximately 1/16th
the time,
or roughly 15 minutes. With roughly 3 hours and 45 minutes of new found “free
time”, it is then possible to scale back to OLTP mode to perform maintenance tasks
such as index reorganization or statistics updating.
Configuration Overview
The Proof of Concept consisted of a 4-node PolyServe Matrix Server cluster for
Windows, running SQL Server 2005 Enterprise Edition, attached to a Fiber Channel
SAN. The servers were commodity dual-processor systems configured with 2GB
physical memory. A PolyServe cluster filesystem was created in a high-performance
cluster volume, created with Matrix Volume Manager, and mounted as drive “S:”
Database Configuration Overview
The database used for the Scalable Shared Database was called debit. The debit
database had a single table, called card, which had 100,000,000 credit card
transactions (see Figure 1). The properties of the primary file for the debit table is
shown to the right, in Figure 2. The card schema is depicted in Figure 3, on the
following page.
The PolyServe cluster filesystem
mounted as S: contained directories for
both the scale-out database and all of
the tempdb databases required by the
scale-out servers; this is a simple way
to deploy Scalable Shared Databases.
Figure 4 shows, simply, how easy it is
to have many tempdb databases
located in a single, high performance
PolyServe cluster filesystem in support
of a large scale-out configuration. In
the example, 4 directories were
created named for each of the servers
(e.g., tmr6s3) used in the Proof of
Concept. The total space consumed by
the card table was roughly 4.3GB.
Performance Results
Using the card table described above,
a set of queries were constructed to
simulate a reporting workload that tests the Scalable Shared Database feature in the
Database Utility model. The queries were constructed to stress all aspects of query
processing.
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Figure 3: Card Table Attributes
These workloads include:
• Physical Disk I/O
o The Query Plans involved full
table scans of 100,000,000
rows
o A full scan of the card table
required 4.3GB of physical disk
reads
• Processor and Memory Utilization
o Data filtering
Processing the WHERE
predicate
o Sorting
o Grouping
o Aggregation
The measured test consisted of executing 8
consecutive ad hoc queries based on the
example listed in the box below. As mentioned
above, the card table was 4.3GB so the total
reporting workload consisted of 34.4GB of
sequential I/O. Randomization of the queries
was achieved by plugging in different values
for m and n in the BETWEEN clause. There
were approximately 1,000,000 unique vendors
stored in the vendor_id column, and 26
transaction types stored in the trantype
column. On average, randomly assigning
values for the BETWEEN clause rendered a dataset of approximately 13,000,000
rows for the sorting, grouping and aggregation tasks.
After the baseline results were collected from 1 server, the PolyServe sql_scale.exe
command was executed to prepare the Scalable Shared Database on 2 servers. The
same 8 queries were then executed 4 per server and complete times measured. The
test was then scaled out to 4 servers where 2 of the 8 reports were executed on
each server and complete times measured.
Between each server count test, the database was transformed from scale-out mode
to OLTP mode and a few more rows were inserted in order to validate the
SELECT vendor_id, avg(amt) avamt FROM card
WHERE trantype BETWEEN m AND n
GROUP BY vendor_id
ORDER BY avamt desc;
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Figure 4: Simplicity of using PolyServe Matrix Server for
tempdb requirements
transformation from Scalable Shared Database mode to OLTP mode. The database
was then transformed once again to a scale-out database on the next number of
servers to be tested (e.g., scaling from 2 to 4 servers). At most only 58 seconds
transpired between measured executions of the query set. That is, no more than 58
seconds was required for the following tasks between measured runs of the
benchmark:
1. Scaling back the database from scale-out read-only mode to OLTP read/write
mode
2. Execute a small number of insertions into the card table
3. Scaling out the database to the next number of nodes (e.g., from 2 to 4).
The task of scaling out the database includes the startup time for all the instances.
Incidentally, with PolyServe’s solution, the instances can be started in parallel on all
servers so the preparation time of the Scalable Shared Database was standardized.
Measured Results
The baseline job complete time
for the 8 queries executed on 1
server was 48 minutes. After
scaling out with the
sql_scale.exe tool and running
4 queries on each of 2 servers,
the job complete time was
reduced to 24 minutes – linear
scalability. Finally, the
sql_scale.exe tool was used to
scale-out to 4 servers. The
same 8 queries were once
again executed, 2 per server.
The job complete time was 14
minutes as depicted in Figure 6.
All told, the scalability from 1 to
4 nodes was 86%.
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Reporting Workload Complete Times
0
10
20
30
40
50
60
1 2 4
Number of Servers
Minutes
Figure 6: Scalability of the Scalable Shared Database on PolyServe Matrix Server
Linear Scalability Requires a Balanced Hardware Configuration
Given the architecture of the Scalable Shared Database, the only component that
can affect scalability is storage bandwidth, as documented in this Proof of Concept at
4 servers. The storage allocated to the small Matrix Server test cluster from the SAN
was sufficient to sustain increased I/O demand from 1 to 2 servers, but I/O latency
increased from 2 to 4 servers. Thus, scalability was slightly affected. Adding disk
capacity in the PolyServe Database Utility for SQL Server is a non-intrusive
adminstrative action so this sort of bottleneck is simple to remedy.
Conclusions
Given ample SAN resources, PolyServe’s implementation of the Scalable Shared
Database delivers linear scalability for SQL Server 2005.
To achieve linear scalability, an appropriate amount of both system and storage
bandwidth must be available to the reporting operations. An individual array,
depending on the vendor, may provide sufficient bandwidth for some applications.
For others, more storage bandwidth may be required.
The Scalable Shared Database option, combined with PolyServe Matrix Server for
Windows Server, included with the Database Utility for SQL Server, provides an easy
way to achieve linear system scalability.
To achieve cost-effective storage bandwidth scalability through software—to scale-
out storage—PolyServe’s Cluster Volume Manager (CVM) may be utilized.
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The Database Utility Overview
Built on SQL Server and Windows Server, PolyServe’s Database Utility for SQL
Server is deeply integrated with both Windows Server and SQL Server. One of the
core products provided with the Database Utility for SQL Server is Matrix Server for
Windows Server.
Matrix Server provides the underlying technology enabling this form of scale-out
reporting. This technology provides the building blocks for shared data. Shared data
means all servers can safely share storage and data on the SAN. PolyServe’s
NTFS-compatible Cluster File System, included with Matrix Server, and designed
using Microsoft’s Installable File System Kit, supports concurrent, direct, read/write
activity through a cache-coherent cluster file system (PSFS). This enables a simple,
one-touch operation for mounting the shared database across multiple servers in the
cluster simultaneously.
Shared data also means all the databases are stored in a single place that can be
accessed by all of the servers simultaneously. This means moving any SQL
database (read-only or read-write) from one server to another can be performed
rapidly, and with minimal storage operator or DBA intervention.
In short, shared data brings the following fundamental benefits:
• A single pool of servers: In this approach, you no longer think of installing a
database on any particular server. Instead, you install into the cluster, and the
database can then run on any server in the cluster. This allows an
administrator to move a database from one server to another in order to
rebalance load and maintain an appropriate level of utilization—without any
need to copy or migrate data. It also means if any server fails, the databases
it had been running can immediately and automatically be restarted on other
machines, ensuring high availability.
• A single pool of storage: Similarly, there is no need to manage storage on a
server-by-server basis and no requirement to have a backup job per server or
separate monitoring for each server’s free space pool. In addition, because
the servers are connected to storage over a SAN, it is easy to provision more
storage when required—but that is only done when the environment as a
whole needs more space.
• Flexibility: A shared data cluster can be formed from servers you already
own. There is no need to buy matched servers; you can mix servers from
different vendors, with different processor types and speeds, different
numbers of processors and different memory configurations. You can even
mix Windows 2000 and Windows Server 2003 in the same cluster, and use
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the shared storage pool to migrate databases to Windows Server 2003
without having to copy data.
• Easy scalability: It is easy to add servers to a cluster if overall demand
grows, and databases can be shifted in a matter of seconds onto newly
added servers with no need for data copying. (Conversely, if workloads drop,
you can shift databases off some of the servers and remove them for
repurposing.) Databases receive full native performance with no virtualization
overhead or virtualization limits, so if a database requires the full speed and
capacity of a large server, it can have it. Once a cluster is created, adding
Scalable Shared Databases becomes as easy as right-clicking and rehosting
a given read-only database to any other server in the cluster.
• Easy high availability: Because all servers have access to all databases,
high availability becomes easy to implement with no requirement for doubling
up hardware. Simply by specifying where a database should be restarted in
the event of failure—from among any of the servers in the cluster—you can
ensure the database will remain available. The shared storage pool requires
none of the complicated and brittle configuration on a server-pair-by-server-
pair basis that traditional failover clustering can entail.
The following section describes the SQL Server-specific components included with
PolyServe Database Utility for SQL Server.
The Database Utility™ for SQL Server Components
The final necessary ingredient to both Scalable Shared Databases and simplified
management of SQL Server is SQL Server integration. The Database Utility provides
an integration layer that applies the core capabilities of Matrix Server and the Cluster
Volume Manager to SQL Server.
This layer, called the Database Utility for SQL Server, includes:
• A SQL Server Health Monitor that periodically probes SQL Server instances
within the cluster to ensure that client requests are being successfully
handled. This will detect if a SQL Server instance hangs, even if the
operating system and hardware remain healthy.
• A SQL Instance Virtualizer that allows the creation of a “Virtual SQL
Server.” A virtual SQL Server is an adaptation of the Matrix Server virtual
host concept. It consists of a virtual IP address that clients use to connect, a
specified primary server in the cluster, a prioritized list of backup servers, and
from one to 16 associated SQL Server instances. If a server fails, the
Virtualizer will move the virtual IP address to the top server in the list that is
capable of hosting the virtual SQL server; it then restarts the database
instances in the new location. Note that, unlike server virtualization, the SQL
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instance Virtualizer component itself is not active during normal operation.
Thus there is no performance penalty; SQL runs at full native speed, with
native access to all hardware resources. The Virtualizer also ensures that a
given database is only ever accessed from one server at a time, since SQL
Server is not designed to allow multiple server concurrent access.
• A SQL Server Registry Replicator. SQL Server stores some configuration
information in the Windows registry, which is located on each server’s
individual C: drive. To ensure this information is available to other servers in
the cluster if a database instance needs to move, the Solution Pack includes
a component that automatically replicates relevant registry information into
the cluster-wide shared storage.
• A SQL Installation and hotfix Updater agent. To simplify installation of
SQL Server and of hotfixes across multiple servers, the Solution Pack
includes a push installer agent. The administrator simply places the
appropriate installation packages in the shared file system, then uses the
push installer agent to perform installations or hotfix updates across the entire
cluster—what PolyServe calls one-click maintenance.
The Database Utility for SQL Server thus provides an easy way to move SQL Server
instances within a cluster to improve resource utilization, an easy path to complete
high availability for all instances in the cluster, and a simple way of performing typical
SQL Server installation and maintenance tasks, all leveraging the core capabilities of
Matrix Server and Volume Manager. The shared data pool provided by Matrix Server
is used to store SQL databases and log files in a single location, accessible to all
servers. The Matrix Volume Manager allows this storage pool to be spread across
space on multiple storage arrays. Matrix Server’s high-availability and application-
control engine ensures that databases remain available regardless of server failures
and, through Dynamic Re-Hosting, allows administrators to adjust work assignments
to maximize utilization. Matrix Manager provides a single point for monitoring and
controlling these elements.
PolyServe’s Cluster Volume Manager
PolyServe’s Windows-based Cluster Volume Manager enables multiple storage
arrays (or storage devices within an array) to be grouped together into scalable,
high-speed, storage pools—available to all SQL Server systems in the cluster.
Matrix Server provides the foundation for the Database Utility for SQL Server by
allowing a set of servers to access shared file systems simultaneously and thus be
managed as a single unit. The Cluster Volume Manager provides an analogous
capability for storage. The CVM allows disk space from multiple storage arrays to be
used and managed as a single pool.
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• With the CVM, an administrator can create a single volume from free space
on multiple arrays (or in multiple LUNs on a single array). In this way a file
system can make use of whatever storage is available.
• The CVM also allows a volume to be striped across multiple arrays. This can
improve I/O rates by aggregating the performance of the arrays, which is
especially useful for sequential workloads frequently associated with data
warehouses.
• Through concatenation or striping, CVM permits the construction of huge file
systems that exceed the typical 2TB limit on the size of individual LUNs.
• In some environments, it is customary to configure every storage array with a
set of LUNs of a fixed size—say, 30 gigabytes. The CVM allows a server
administrator to construct file systems of whatever sizes are desired using
these fixed LUNs.
• Finally, if a file system is becoming too full, the CVM can be used to expand
the file system, without taking the cluster down, using free space from any
array accessible to the cluster.
If the storage ever becomes a bottleneck, as it did in the POC, the Volume Manager
enables multiple storage devices—controllers, cabinets, or arrays—to be aggregated
together into high-performance shared storage pools. Once these pools are created,
the volume manager can be used to stripe across each volume (LUN) to effectively
aggregate the bandwidth across each device. Thus, if a single shared pool was
composed of two LUNs, each located on a separate array, the logical, shared
volume could span both arrays, aggregating the performance of each array (across
spindles, controllers, and paths to the cluster attached to the storage).
Like all other aspects of the Database Utility, the CVM is managed cluster-wide from
a single control point. Thus, just as Matrix Server allows servers’ data sets to be
handled in a unified way, the Volume Manager allows the physical storage resources
associated with a cluster to be used and managed as a single entity.
Summary
Microsoft SQL Server 2005™ Enterprise Edition now supports scale-out reporting
through Scalable Shared Databases. Scale-out reporting enables multiple SQL
Server 2005 systems to mount a read-only copy of a database.
When deployed using PolyServe’s Database Utility™ for SQL Server, Enterprises
may achieve linear scalability of SQL Server for reporting, reduce reporting times up
to 16x, and eliminate manual storage configuration processes.
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This proof of concept (POC) demonstrates PolyServe’s solution for the Scalable
Shared Database. The POC consists of a 4-node PolyServe Matrix Server cluster
running PolyServe’s Database Utility for SQL Server and Microsoft SQL Server 2005
Enterprise Edition, connected to a SAN.