Datasheet

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CHAPTER 1 What Kind of Protection do You need?
Availability vs. Protection
No matter how frequently you are replicating, mirroring, or synchronizing your data from the disk,
host, or application level, the real question comes down to this:
Do you need to be able to immediately leverage the redundant data from where it is being stored,
in the case of a failed production server or site?
If you are planning on resuming production from the replicated data, you are solving for
•u avail-
ability and you should first look at the technology types that we’ve already covered (and will
explore in depth in Chapters 5–9).
If you need to recover to previous points in time, you are solving for •u protection and should first look at
the next technologies we explore, as well as check out the in-depth guidance in Chapters 3 and 4.
We will put the technologies back together for a holistic view of your datacenter in Chapters 10–12.
Overview of Protection Mechanisms
Availability is part of the process of keeping the current data accessible to the users through
Redundant storage and hardware
•u
Resilient operating systems•u
Replicated file systems and applications•u
But what about yesterday’s data? Or even this morning’s data? Or last year’s data? Most IT
folks will automatically consider the word backup as a synonym for data protection. And for this
book, that is only partially true.
Backup Backup implies nightly protection of data to tape. Note that there is a media type
and frequency that is specific to that term.
Data Protection Data protection, not including the availability mechanisms discussed in
the last section, still covers much more, because tape is not implied, nor is the frequency of
only once per night.
Let’s Talk Tape
Regardless of whether the tape drive was attached to the administrators’ workstation or to the
server itself, tape backup has not fundamentally changed in the last 15 years. It runs every night
after users go home and is hopefully done by morning. Because most environments have more
data than can be protected during their nightly tape backup window, most administrators are
forced to do a full backup every weekend along with incremental or differentials each evening
in order to catch up.
For the record, most environments would likely do full backups every night if time and money
were not factors. Full backups are more efficient when doing restores because you can use a single
tape (or tapes if needed) to restore everything. Instead, most restore efforts must first begin with
restoring the latest full backup and then layer on each nightly incremental or latest differential to
get back to the last known good backup.
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