White Paper

Cost and Performance benefits of Dell™ Compellent™ Automated Tiered Storage for Oracle® OLAP
Workloads
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Data Instant Replays
Dell Compellent Data Instant Replay technology plays a key role in delivering outstanding performance
in an automated tiered storage environment. Data Instant Replay protects data without wasting
capacity. You create space-efficient snapshots (Replays) of changes in data for continuous protection
from loss or corruption. Replays use minimal storage space because only data written to the volume
since the previous Replay was taken is captured on the array.
In the Dell Compellent architecture, new data is written by default to tier 1, RAID 10 storage to
provide the best write performance. Over time, according to the Storage profile, infrequently accessed
blocks of data are moved to a lower storage tier and RAID level, or to a different RAID level within the
same tier. Moving this read-only data from RAID 10 to RAID 5 within the same tier enables the solution
to maintain the same read performance. Whether data is moved to a new tier or RAID level, the
migration frees up space on the higher tier or RAID level. When new data is written to an existing block
that was converted to read-only and migrated to a lower tier, those writes are redirected to the tier
1, RAID 10 storage. A new writable block is automatically allocated to provide the highest transaction
performance.
Snapshot blocks are periodically moved to the lower tiers Figure 4.
Fast Track
Dell Compellent Fast Track boosts automated tiered storage by delivering optimal placement of data
on each individual disk. Fast Track uses the intelligence continuously collected by the Dell Compellent
system to identify the most active, frequently accessed blocks of data on each spindle. It then places
those data blocks together on the outer tracks of each drive. Keeping the head focused on that one
area of the disk, where the active data resides, and delivers better performance than if the head was
forced to move all over the disk.
Fast Track works on every spindle-based drive type within the system. Data movement happens
automatically, on a daily basis, without any manual intervention. With Fast Track, organizations
optimize performance of each platter based on actual usage patterns, reducing seek times for the most
active blocks of data. Fast Track also helps reduce long-term storage costs by maximizing performance
on cost-effective drives.