Storage Cat 08 3/10/08 17:07 Page 39
39 ADVERTORIAL
Q
land in full on disk before initiating the deduplication process. data is too big to fit in RAM unless it is a very small
deployment. So it needs to seek on disk, and disk seeks are
7. How does deduplication improve off-site replication and DR? notoriously slow (and not getting better).
The effect deduplication has on replication and disaster The easiest ways to make data deduplication go fast are (1)
recovery windows can be profound. To start, deduplication to be worse at data reduction, e.g. look only for big
means a lot less data needs transmission to keep the DR site sequences, so you don’t have to perform disk seeks as
up to date, so much less expensive WAN links may be used. frequently; and (2) to add more hardware, e.g. so there are
Second, replication goes a lot faster because there is less more disks across which to spread the load. Both have the
data to send. The length of the deduplication process (beginning unfortunate side effect of raising system price, so it becomes
to end) depends on many variables including the deduplication less attractive against tape from a cost perspective. Vendors
approach, the speed of the architecture and the DR process. vary in their approaches.
For the most efficient time-to-DR, inline deduplication and
replication (inline) of deduplicated data will yield the most 9. How much “upfront” capacity does deduplication require?
aggressive and efficient results. In an inline deduplication This is not a question for inline deduplication systems, but it is
approach, replication happens during the backup, significantly for a post-process. Post-process methods require additional
improving the time by which there is a complete restore point at capacity to temporarily store duplicate backup data before the
the DR site, or improving the time to DR readiness. dedplication process begins.
8. How will data deduplication affect my backup and 10.What are best practices in choosing a
restore performance? deduplication solution?
Restore access time will be faster than tape, since it is online • Ensure ease of integration to existing environment.
and random access. Throughput will vary by vendor. Data • Get customer references - in your industry.
deduplication is a resource-intensive process. Before it • Pilot the product/technology - in your environment.
writes data to disk, it needs to find whether some new small • Understand the vendor's roadmap.
sequence of data has been stored before, often across
hundreds of prior terabytes of data. A simple index of this See Data Domain on stand 280
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