Best_Practices_MS_Exchange_Server.pdf

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Paragon Drive Backup Enterprise Server
Edition
Best Practices for MS Exchange Server
Drive Backup Enterprise Server
2
Best Practices for MS Exchange Server
Contents
1
Introduction..................................................................................
4
1.1 About Drive Backup
....................................................................................... 4
1.2 Backup Concepts...........................................................................................
4
1.2.1 File-Level Backup and Volume Imaging
.............................................................................4
1.2.2 Data Consistency
.............................................................................................................4
1.2.3 Offline and Online Backup
................................................................................................4
1.2.4 Snapshots
.......................................................................................................................5
1.2.5 Copy-On-Write
.................................................................................................................5
1.2.6 Data Synchronization
.......................................................................................................6
1.2.7 Write Inactivity Paradigm
..................................................................................................7
2
Technology Overview
................................................................... 7
2.1 Paragon HotBackup Description.....................................................................
7
2.1.1 Hotbackup Concepts
........................................................................................................7
2.1.2 How it Works
...................................................................................................................7
2.2.1 VSS Concepts
.................................................................................................................8
2.2.2 How it Works
...................................................................................................................9
2.2.3 MS VSS Limitations..........................................................................................................9
2.3.1 Enabling Backup via VSS
.................................................................................................9
2.3.2 How it Works
................................................................................................................. 10
2.2 MS VSS Basics
.............................................................................................. 8
2.3 How Drive Backup Integrates with MS VSS
..................................................... 9
2.4 Choosing between Online and Offline Backup...............................................10
3
Protecting Microsoft Exchange Server
........................................ 10
3.1 Microsoft Exchange Server Storage Management Overview
..........................11
3.1.1 Exchange Storage Components......................................................................................
11
3.1.2 Exchange Files
.............................................................................................................. 12
3.1.3 Transaction Logs............................................................................................................
13
3.1.4 Clean Shutdown State
.................................................................................................... 14
3.1.5 Log Truncation
............................................................................................................... 14
3.1.6 Data Restoration and Rolling Forward
............................................................................. 14
3.1.7 Performance
.................................................................................................................. 16
3.1.8 Reliability.......................................................................................................................
17
3.1.9 Backup
.......................................................................................................................... 17
3.2 Backing up Exchange Databases with DBE...................................................17
3.2.1 Recommended Backup Options
...................................................................................... 18
3.2.2 Recommended Information Store Layouts
....................................................................... 18
3.2.3 Unsupported Database Layouts
...................................................................................... 19
3.3 Restoring Exchange Databases with DBE
.....................................................20
3.4 Choosing between Hotbackup and VSS Online Backup Options
....................20
3.5 How to Use DBE for Protecting Exchange Data
.............................................21
3.5.1 How to Redistribute Exchange Data
................................................................................ 21
3.5.2 How to Backup Exchange Data
....................................................................................... 24
3.5.3 How to Restore Exchange Data
...................................................................................... 28
3.5.4 How to backup and restore Exchange databases distributed across multiple volumes
........ 34
4
Appendix....................................................................................
39
Drive Backup Enterprise Server
3
Best Practices for MS Exchange Server
4.1 RAID levels
..................................................................................................39
4.2 Exchange Disaster Recovery and Troubleshooting Resources
......................40
Drive Backup Enterprise Server
4
Best Practices for MS Exchange Server
1 Introduction
This paper addresses various aspects of a Microsoft Exchange Server data protection by using Paragon Drive
Backup Enterprise (DBE). It describes the concepts, limitations and best practices for Paragon Drive Backup
Enterprise to protect "no downtime" operational solutions based on Microsoft Exchange Server. All
mentioned recommendations are generic and not specific for a certain Exchange Server configuration.
1.1 About Drive Backup
Paragon Drive Backup Enterprise is a backup tool that implements the best of volume imaging techniques for
reliable, fast and convenient data backup and restoration. The program includes end-user tools for building
and automating recovery and replication procedures. It implements high-performance algorithms for
intelligent data analysis and processing, provides an optimized manipulation for a large set of filesystems
that covers all popular filesystems for Windows and Linux platforms and more features.
1.2 Backup Concepts
1.2.1 File-Level Backup and Volume Imaging
There are two concepts about backup subject. A
file-level backup
is oriented to store separate files. A
volume-level backup
or
imaging
is oriented to store whole filesystem of a volume.
A
file-level backup
naturally provides an intuitive and flexible way to select objects to store. File-oriented
backup tools allow choosing any combination of both local and networking accessible files. A file-level data
restoration allows to selectively restore only damaged files without affecting other ones. However, there are
important file-related system objects which are not files and usually cannot be stored, restored and even
accessed from a file level.
A
volume imaging
can store any metadata associated with files including distribution information, security
data, quotas, extended attributes, named streams, multiple hard and symbolic links and so on. Disk imaging
tools generally provide higher backup performance because they do not involve filesystem drivers to the
process. In addition, imaging tools can backup offline filesystems and even ones not being supported by a
host operating system. A data restoration generally does not require a host operating system to run, so that
volume-imaging technique is a perfect choice for system cloning and disaster recovery tools. Disadvantages
of volume imaging are that it cannot be applied to remote resources and a general ineffectiveness of backup
and restore of selective files within the volume-imaging framework.
1.2.2 Data Consistency
The fundamental requirement to backup is saving of
data consistency
. This means that if applications are
stopped, and data are restored, and applications are restarted, they will run smoothly with restored data.
A
data consistency
is conditionally divided into a
physical
and
logical
consistency. A
physical consistency
means storing information about involved data files and file-related attributes in a state that is interpreted by
applications as "integral", or "valid", or "repairable on-the-fly". A
logical
consistency means an application-
level correctness of stored business data. An automatic correction of minor inconsistency of business data is
usually provided by the
transactions mechanism
, which is the basis of modern technologies of information
processing.
1.2.3 Offline and Online Backup
As regards to the data consistency concept, offline data are in consistent state (with the only condition that
an application or a system was shut down correctly). Offline data archiving is referred to as
offline backup
.
Its advantages are ensured data consistency, increased backup speed (due to absence of concurrent data
access), resource saving and low impact to a system performance.
The disadvantage is that offline backup is not applicable for "24x7 availability" systems. For continuously
working systems
online backup
methods should be applied.
Drive Backup Enterprise Server
5
Best Practices for MS Exchange Server
1.2.4 Snapshots
The great challenge to online backup is to provide a coherent state of all open files and databases involved
in a backup, under the condition that applications may continue writing to a disk.
The "volume snapshot" concept has met that challenge. A
snapshot
is a point-in-time copy of a volume
involved to a backup process. It must be quickly created at a period when applications do not write to disk.
Once snapshot has been created, a backup utility copies data from it while applications continue working
with an original volume. Modern snapshot technologies reduce
backup window
down to few seconds.
There are hardware and software based snapshot solutions.
Hardware snapshots
such as the
Split-Mirror
technique instantly provide an independent copy of a whole data set; they make no impact to the system
performance and can participate in off-host backup solutions. Disadvantages are that hardware snapshots
are naturally hardware-dependent, double requirements to storage resources and some time is required in
order to re-synchronize a hardware snapshot after it has been used, with the actual disk data.
Instead,
software snapshots
are hardware-independent and resource-saving solutions. The disadvantage is
that they cannot make a copy of a whole data set instantly, so that they run and make additional computing
load to a host system until a backup routine is ended and a snapshot is destroyed.
Unlike hardware snapshots, types of software snapshots, which are used in practice, are not independent
from original data. In case an original volume fails, all of its snapshots fail as well. Software snapshots do
not really protect data; they are used as supplementary mechanisms in backup solutions.
Paragon Drive Backup provides the original online backup technique (named
HotBackup
) and supports any
snapshot technologies that can participate in the MS VSS framework.
1.2.5 Copy-On-Write
The
Copy-On-Write
(COW) method predominates among software snapshot techniques. It is based on the
idea of preserving original contents of modified blocks before modifications are written to a disk, in special
difference storage
. COW maintains an original volume in the actual state and stores its original content at
the moment of snapshot creation in the difference storage.
A system-level agent, which is responsible for snapshot maintaining, must keep track of all changes being
made on a volume. On first attempt to overwrite a block, the snapshot agent copies original block's content
to the difference storage and then allows modifying that block. When a backup utility acquires some block
from the snapshot, the agent determines its status and takes a "changed" block from the difference storage
while "unchanged" block is taken from the original volume. The following illustrates COW basics:
1. A volume was partially in use. Blocks A, B, C, and D contained data. A COW based snapshot was created
for this volume. The snapshot provider watches only the used blocks of a volume. Initially they are
marked as "unchanged".
A
B
C D
Original contents of a volume
unchanged
unchanged
unchanged
unchanged
Status of blocks in the snapshot
unused
unused
unused
Difference storage content
(currently nothing)
Contents of the snapshot
A
B
C D

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