Mosaic Technology’s IT Director’s Series:
Exchange Data Management:
Why Tape, Disk, and Archiving Fall Short
Mosaic Technology Corporation * Salem, NH (603) 898-5966 * Bellevue, WA (425)462-5004
Mosaic IT Director’s Series
Exchange Data Management
Exchange Data Management:
Why Tape, Disk, and Archiving Fall Short
Introduction......................................................................................3
Tape Backup Challenges .....................................................................4
Full Database Recovery ...................................................................5
Mailbox Recovery............................................................................6
Message Recovery ..........................................................................6
Pros and Cons of Tape Backup Methods .............................................7
Challenges of Disk-Based Backup.........................................................8
Backup to Disk ...............................................................................8
Continuous Data Protection ..............................................................8
Snapshot-Based Backup ..................................................................9
Application Intelligence....................................................................9
Pros and Cons of Disk-Based Backup Methods................................... 10
E-mail Archiving .............................................................................. 11
Benefits of E-mail Archiving............................................................ 11
Challenges of E-mail Archiving........................................................ 11
The Challenge of Managing Multiple Products....................................... 12
Next Generation Data Management for Exchange ................................. 14
Conclusion...................................................................................... 15
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Introduction
Email has become the number one method of business communication,
exceeding even the telephone in importance within an organization. It is a
key application in corporate data centers and email servers contain an
increasing percentage of corporate data assets.
As a result, email is now the mission critical application for enterprises. With
this growth in importance comes a challenge for IT administrators - ensuring
that in the event of errors or failures, email can be recovered and restored as
soon as possible.
For many years, traditional backup products tried to address the challenges
that come with protecting and recovering e-mail messages. The advent of
Exchange 2000 and 2003 brought increases in Message Store size and a
scalability challenge for many organizations. Traditional tape backup methods
can no longer capable of keep up with the increased size of Message Stores
and limited backup window. Recent regulations (SEC, HIPAA, SarbanesOxley, etc.) that require organizations to archive e-mail add to the problem.
This paper reviews traditional data protection and e-mail archiving methods
and describes their pros and cons with respect to managing Exchange.
Mimosa Systems believes that the challenges that you are facing to manage
Exchange can be solved with a new breakthrough approach to Exchange data
management.
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Exchange Data Management
Tape Backup Challenges
For the majority of organizations, tape backup is the preferred solution to
protect Exchange. With tape you can use NTBACKUP.EXE, the free backup
utility provided by Microsoft, or you can use one of the popular third-party
backup products.
These tape backup products perform online backup of Exchange and stream
data from the Exchange database to tape media at high speeds. Using the
Exchange Backup API (ESE – Extensible Storage Engine), third-party
products perform a full backup of Exchange including all databases and log
files.
With Exchange 5.5, there was one Exchange database per server -- by
default a full backup protected the entire 5.5 Server. Exchange 2000 and
2003 introduced the storage group concept. Exchange 2000/2003 Servers
can have up to four storage groups. Each storage group can contain up to
five databases. Exchange 2000/2003 full backups are performed at the
storage group level because a storage group shares the same log file for all
the databases it contains. As with Exchange 5.5, it is important to copy the
complete log files with each backup.
Figure 1: Traditional Tape Backup Schedule.
Standard practice dictates a weekly full backup of Exchange. Each day an
incremental Exchange backup is performed to copy new log files. (figure 1.)
After the backup completes log files are truncated. Optionally a differential
backup makes a copy of new log files created since the last full backup, but
does not truncate the logs.
In the event of a recovery, the full backup tape is restored followed by the
incremental backup tapes. Recovery time increases with the number of tapes
to restore, so many users prefer a daily full backup of Exchange if their
backup window permits.
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Exchange Data Management
Full Database Recovery
Traditional tape backup methods allow for full recovery of the Exchange
database(s). In the event of a hardware failure or corrupt database, the
entire Exchange database can be restored from tape. (figure 2.)
Recovery time depends on the amount of data contained in the Exchange
database. As a rule of thumb, recovery time is two to three times the amount
of time it takes to perform the backup. For a typical 40 GB Exchange
database, backup time is one to two hours and the recovery time is two to
six hours, depending on the amount of log files.
For most organizations, going without e-mail service for greater than two
hours is unacceptable. One alternative is to use a Recovery Server. A
Recovery Server is a complete Exchange Server running in standby, ready to
take over e-mail services when the primary Exchange Server fails. New in
Exchange 2003 is a Recovery Storage Group. A Recovery Storage Group is a
storage group that is available to take over temporary e-mail services when
a primary storage group fails.
It is essential that you protect Exchange from a total system failure and can
restore a complete Exchange database. However, the most common errors
that impact Exchange are not system hardware failures, but human errors.
A common system administrator error is to inadvertently delete a user
mailbox. If a large number of mailboxes are active it is easy to confuse
mailboxes and delete one by mistake. The Exchange Backup API supports full
Exchange database backup only and does not support mailbox restore;
therefore, some interesting methods have been developed to recover a lost
mailbox.
Figure 2: Typical Exchange Full Database Recovery.
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Exchange Data Management
Mailbox Recovery
Using Exchange 5.5, a common method to recovery a mailbox is to restore a
full database backup to a Recovery Server. This requires a dedicated server
which may be cost prohibitive to some organizations.
Microsoft added a Mailbox Recovery feature in Exchange 2000 and 2003. It
lets you configure a set period of time for deleted mailboxes to remain on the
Exchange Server. Normally a setting of 30-days gives you plenty of time to
recover a mailbox deleted by mistake t.
Beginning with Exchange 5.5, third-party backup vendors devised a method of
mailbox backup by introducing a second backup pass at the mailbox level. This
method uses the Microsoft Message API (MAPI) and is commonly referred to
as “Brick-level Backup”.
There is a drawback to this method -- the second-pass of the Exchange
Database places a very large burden on the Exchange Server CPU. It takes four
to eight times as long to perform a brick-level backup as it takes to perform a
full backup. In many cases, the brick-level backup alone can take longer than a
24 hour back up window. Due to these penalties, the majority of users do not
perform brick-level backups. They rely on the Mailbox Recovery feature to
restore deleted mailboxes in Exchange 2000/2003 and use a Recovery Server in
Exchange 5.5. (Figure 3.)
Figure 3. Typical Exchange Mailbox Recovery
Message Recovery
It is common for end users to delete e-mails by mistake. The Outlook client
provides a Deleted Items folder for message recovery, but if this folder is
emptied, help is required. No practical tape backup method exists for
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Exchange Data Management
message level recovery. It is not supported by the Exchange Backup API.
Third-party brick-level backup methods are too slow to be practical.
General practice is to configure the Exchange Server Deleted Item Folder to
30 days to allow for message recovery. After 30 days messages are simply
not recoverable. Backup tapes can be restored to a Recovery Server for
message recovery, but this time consuming process is only practical in
special situations or for special individuals (e.g. company executives, legal
searches, etc.).
Pros and Cons of Tape Backup Methods
The advantage of tape backup is that the technology is mature, performs
well, and is fully supported by Microsoft for full Exchange backups. If the
Exchange database is not too large (< 40GB) backups can be performed in a
reasonable amount of time allowing for daily full backups. For large
databases, incremental backups can be used, but this increases total
recovery time. Another advantage is that tape backups can be transported
offsite for disaster recovery.
A disadvantage of daily full backups or daily incremental backups is that the
amount of data that can be lost is potentially 23 hours of data. The period of
time where data is not being protected defines your Recovery Point Objective
(RPO). Depending on the needs of your organization, this may be
unacceptable. A second disadvantage of tape backup is the slow recovery
time. Depending on your backup scheme, tape recovery can take hours
increasing your Recovery Time Objective (RTO). If brick level backups are
not performed, mailbox or message level restores can take many more
hours. Depending on the needs of your organization, this may also be
unacceptable.
Cons
Pros
Mature and stable technology 23 hour RPO
Suitable for small databases Slow total recovery (RTO)
Offsite storage for DR
Not suitable for large databases
Limited mailbox recovery
Complex and error prone
Figure 4. Pros and Cons of Traditional Tape Backup
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Challenges of Disk-Based Backup
The disadvantages of tape backup are reasonably controlled with Exchange
5.5 due to the single database per server architecture of Exchange 5.5. The
size of each Exchange Server is limited by processing power and storage
capacity, which limits the backup window and recovery time. Many
organizations deployed additional 5.5 servers to compensate for email
growth and shrinking backup windows. This added cost and complexity for
dealing with multiple Exchange Servers.
With the introduction of Exchange 2000 and 2003, Exchange Servers
Message Stores have grown significantly to support more mailboxes per
server and increased the backup window and recovery time. New methods
for Exchange data protection are necessary to allow for acceptable recovery
times.
Backup to Disk
A common method to reduce the backup and recovery time is to use disk as
the backup target in place of traditional tape media. Leading third-party
backup vendors offer this capability for large Exchange databases whose
backup window is too small to complete full backups to tape. These solutions
successfully reduce the time to perform a full backup and fit the backup
window. Full database recovery performance is also improved. By leveraging
new “cheap disk” technology, these disk-based backup solutions are adopted
by users with very large Exchange databases who want fast backup and
recovery.
Disk-based backup improves total recovery time, but they continue to use
the Exchange Backup API and MAPI for brick-level backups. These data
streams are optimized for linear tape and do not take advantage of the
random read/write capability of disk. This adds overhead and does not
optimize the data for quick restores. Disk-based backup methods the same
as tape and do not reduce the 23-hour window that Exchange data is
unprotected.
Continuous Data Protection
Continuous Data Protection (CDP) is disk-based backup designed to protect
Exchange in near real-time. It uses a replication agent (device driver) that
sits on the Exchange Server (very low in the processing stack) and creates a
100% copy (mirror) of the Exchange Server. After the initial mirror, the
software replicates block-level changes to the files. This allows for real-time,
up-to-the-minute backup of the Exchange Server.
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Exchange Data Management
The host mirror can be installed locally or remotely depending on the disaster
recovery strategy. In the event of system hardware failure (or site disaster)
the host mirror can take over Exchange services. A CDP solution is complex
and is used by organizations that require the most available Exchange
services. Full tape backups are still necessary to maintain a point-in-time
copy of Exchange. For example, should the Exchange database be corrupted,
a tape backup is necessary for recovery because the host mirror is also
corrupted. Full backups can be performed on the “split-mirror” which avoids
any backup window problems.
Snapshot-Based Backup
Snapshot-based backup methods are an alternative to CDP and provide
multiple recovery points. Snapshots use a low-level agent that sits on the
Exchange Server and protects data using a “copy-on-write” method. As new
blocks are written to the primary volume, the original blocks are first copied
to the snapshot volume. This snapshot volume can be on the same local
array or on a remote array.
Snapshots protect only changed data and do not protect the data on the
primary volume. For logical errors, snapshots are an efficient method of data
protection. Snapshots can be taken hourly, for example, and reduce the RPO
for Exchange. The Exchange Server can be “rolled back” to an earlier point in
time to recover from a database corruption event. For protection from a
system crash, full tape backups remain necessary to protect data on the
primary volume. The backup can be performed using the snapshot to reduce
the backup window.
Application Intelligence
The major disadvantage of CDP and snapshot-based backup methods is they
use low-level agents that operate in the Exchange Server to intercept blocks
as they are written to disk. Because they operate at such a low level, they
have no understanding of the data the blocks contain. If corrupt data is
introduced on the Exchange server, it is simultaneously introduced on the
disk-based replica, rendering it useless.
This concept of understanding the data is called Application Intelligence. The
tape-based and disk-based methods that use the Exchange Backup API are
application intelligent and can detect data corruption. They can also be used
to perform mailbox or message level recovery. The replication technologies
that copy the blocks for CDP and snapshot cannot detect data corruption and
are only useful for full system recovery.
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Pros and Cons of Disk-Based Backup Methods
Disk-based backups use storage media which performs faster than traditional
tape storage media. As a simple substitute for tape media, full Exchange
database backups and recovery times can be improved dramatically using
disk. CDP delivers the highest availability and is valuable to organizations
that require near real-time recovery for Exchange. Snapshot-based backup
methods offer an efficient means to reduce the RPO for Exchange.
CDP disk-based backup methods are deficient because they require a lowlevel host agent be installed on Exchange to intercept blocks of data. They
are also not application intelligent. This renders them ineffective if data
corruption occurs and makes them inflexible for mailbox or message level
recovery.
Disk-based backup methods cannot protect Exchange in all recovery
situations – crash recovery, corruption recovery, mailbox recovery and
message recovery. Combining multiple tape and disk-based recovery
methods adds complexity and increases the chance of error.
Pros
Reduce Exchange RTO
CDP offers near real-time recovery
Reduce Exchange RPO
Useful for large databases
Avoid backup window problems
Cons
Low-level agents installed on Exchange Server
No mailbox or message recovery
No data corruption detection
Full tape backup still required
Complex and error prone
Figure 5. Pros and Cons of Disk-Based Backup Methods
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Exchange Data Management
E-mail Archiving
E-mail archiving applications have received much attention in recent years
due to the number of organizations fined for not properly preserving e-mail
records. Because e-mail contains valuable company information, it must be
preserved just like other paper company records. Financial institutions that
are governed by SEC Rule 17a-4 are required to archive e-mail. All public
corporations are also required to preserve e-mail records according to the
Sarbanes-Oxley Act of 2002 as are other organizations in healthcare,
government and bioscience.
Benefits of E-mail Archiving
The primary benefit of e-mail archiving is the preservation of company e-mail
in a separate database that is designed to be scalable and allow fast search
and retrieval. By indexing all incoming messages, full-text searches can
quickly scan the entire archive for messages or attachments. These searches
can be performed by authorized staff to comply with legal or regulatory
investigation or by company employees searching for old e-mail. E-mail
preservation and fast accessibility are two major benefits of e-mail archiving
that go beyond the functionality that Exchange offers.
E-mail archiving also provides Mailbox Extension. Mailbox Extension is
Hierarchical Storage Management (HSM) technology that removes
attachments in Exchange and replaces them with a “short-cut”. The originals
are stored in the archive and are accessible by users from Outlook.
The major benefit of Mailbox Extension is that attachments that normally
occupy storage on Exchange can be relocated to the archive and the
Exchange database size can be reduced dramatically – by as much as 80%. A
smaller Exchange database means you can increase mailbox quotas (or
eliminate them all together) and reduce the use of .pst files. Users can take
advantage of the extra mailbox space to store old e-mail – a feature referred
to as the “infinite mailbox”.
Challenges of E-mail Archiving
The basic challenge of e-mail archiving is that it must be managed in addition
to protecting Exchange. It’s a standalone application. Time managing e-mail
archiving is additional to the workload required to manage Exchange backup
and recovery. E-mail archiving maintains an archive of Exchange data.
However, this data is only used for archive search and retrieval. It is not
used for data protection. Traditional tape backup methods are still required
for full Exchange database protection.
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Exchange Data Management
A second challenge of e-mail archiving is that it uses the Microsoft Message
API (MAPI) to read Exchange and extract message information. MAPI, as
discussed previously, is slow and CPU intensive. Exchange Server
performance suffers anytime MAPI is used to read its database. Archive
Window is a new term that represents the impact e-mail archiving has on
Exchange. Best practice is to run MAPI on the weekend to capture messages
for archive and not burden Exchange Server during the week when usage is
high.
Because the archive server only reads Exchange once a week, messages
deleted from the Exchange Server during the week are not captured.
Therefore, e-mail archive for compliance relies on Exchange Journaling to
capture e-mail during the week.
Exchange Journaling is a native feature of Exchange that makes a copy of all
e-mail for any assigned mailbox. It stores the e-mail in a separate journal
folder. Journaling is a reliable method to capture 100% of e-mail but it
introduces its own CPU burden and storage burden on Exchange. For this
reason Exchange Administrators are very wary about using Journaling.
Cons
Pros
Reduces compliance risk
Preserves e-mail
Full-text search of e-mail
Reduces Exchange database size
Reduces need for mailbox quotas
and .pst files
Stand alone application
Additional hardware and software costs
Burdens Exchange CPU with MAPI; archive
window problem
Requires Journaling which introduces additional
burden on Exchange
No integration with backup
Figure 6. Pros and Cons of E-mail Archiving
The Challenge of Managing Multiple Products
Managing Exchange data using multiple data management products creates
its own challenges. Depending on the size of your Exchange database(s) and
the RTO and RPO requirements of your organization, you may need multiple
products to meet your service level agreements. The most obvious problem
is the increase in management complexity -- multiple products, multiple
consoles, multiple servers, multiple storage areas and multiple storage
formats. You will be challenged to manage all these products, and in the
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Exchange Data Management
event of a system crash, you will be challenged to perform a system recovery
in the least amount of time – not an easy task!
Another disadvantage of multiple data management products is the
cumulative demands they place on your Exchange Server. Depending on the
method used to interface with Exchange, MAPI places a significant burden on
the Exchange Server CPU. Your Exchange Server needs to be running at full
capacity 24x7 and provides better performance with less CPU competition
from third-party products. Each third-party product installs its own agent on
Exchange to manage data transfer. Multiple agents add risk and complexity
to your Exchange Server.
Finally, using multiple data management products makes it impossible to
manage Exchange data for retention and disposition. New legal and
regulatory requirements make it necessary to preserve e-mail for a specific
time period, and to dispose of e-mail when it is no longer needed.
When e-mail data exists in multiple locations, in multiple formats, it is
difficult to manage. Each independent product protects its copy of the data
and has no notion of being integrated with other products for the single
purpose of retention and disposition. This situation places your organization
at risk of expensive legal discovery and regulatory penalty.
Product
Full Tape
Backup
Brick-level
Tape Backup
Continuous
Replication
Copy-onWrite
Snapshot
E-mail
archive
Full
Mailbox
Recovery Recovery
Message
Recovery
Search Retention
Discovery Disposition
Mailbox
Extension
Yes
No
No
No
No
No
No
Yes
Yes
No
No
No
Yes
No
No
No
No
No
Yes
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Figure 7. Comparison of Exchange Data Management Products
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Exchange Data Management
Next Generation Data Management for Exchange
Mimosa Systems designed Mimosa NearPoint for Microsoft® Exchange
Server, to address the many challenges that face Exchange data
management. NearPoint dramatically improves recovery time and reduces
the recovery point with near continuous data protection. It also provides email archiving in a single-integrated solution. Mimosa did not believe that a
separate stand-alone application was required for e-mail archive. In fact,
data protection and e-mail archive applications can be served simultaneously
with a single Indexed Object Repository. Administrators, users and auditors
all enjoy self-service access to the Indexed Object Repository using standard
Microsoft Outlook and OWA interfaces. Complete mailboxes can be browsed
and searched at any point-in-time to find lost e-mail or to retrieve complex
e-mail history information for legal discovery.
The Mimosa NearPoint software solution, based on standard Microsoft
technologies, runs on a standard Intel server. It is application-intelligent
providing deep integration with Exchange and Outlook. NearPoint is diskbased and leverages commodity storage, such as SATA RAID and NAS
appliances, to provide near real-time data protection and access to archived
data from multiple Exchange Servers. Deployment is easy since there is zero
foot print on Exchange Servers and desktops. Mimosa provides users and
auditors instant search and access to email that has been protected,
archived, and extended via a standard Microsoft Outlook or Outlook Web
Access user interface.
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Exchange Data Management
Figure 8. Mimosa NearPoint Architecture
Conclusion
The challenges of managing Exchange are complex and involve the use of
multiple independent and costly data management products. Traditional tape
backup methods provide full Exchange database protection; however they
are limited by slow recovery time, a 23-hour recovery point and for all
practical purposes no mailbox or message level recovery.
Disk-based backup methods reduce Exchange recovery time and the
recovery point but they are kernel intrusive, suffer from data corruption
problems and do not support mailbox or message level recovery.
Depending on your particular recovery requirements, multiple backup
products may be necessary to achieve your overall recovery service
objectives with added complexity and cost. E-mail Archiving is another MAPI
driven application that increases the load on your Exchange Server and
further increases the demand for already stretched budgets and
administrator’s time.
Mimosa NearPoint for Microsoft Exchange Server is a next generation data
management solution for Microsoft Exchange that combines immediate finegrained recovery, mailbox extension and archiving in a single solution.
NearPoint delivers in a single-integrated solution features that are typically
found in multiple products.
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