This is the fifth of eight in a series titled 8 Must Haves for the IT Director

Number 5 – Space-Efficient Snapshots

The hidden cost of snapshot space hogs

Using snapshots to protect array data is nothing new. What is new is how the aging (or tiered progression) algorithms associated with primary data can also be applied to snapshot data. There are 2 parts to snapshot efficiency; 1) minimizing the amount needed initially and 2) placing the older snapshots on lower tiered groups of disks.

Some storage architectures implement snapshots using large chunks, or pages, of data. These larger block approaches tend to overuse snapshot space by preserving data at a minimum of 15K chunks. Imagine a 15K snapshot for a single byte change. Compellent snapshots can be configured from 512 Byte blocks to 4K, drastically reducing the per change overhead.

Snapshot migration reduces costs

The second snapshot efficiency gained by the Compellent architecture is that, similar to primary data, snapshot data can also be progressively moved to lower speed, lower cost media as it ages. Snapshots for yesterday are generally more likely to be needed than snapshots from a previous month, especially for high-IO applications. Thus, it makes sense that the most recent snapshots are readily available on the fastest tier groups; a process handled automatically by Compellent.

Since Replays are so space efficient, recovery can take as few as 10 seconds and volumes can be
mapped to any server without disruption. To simplify the process, administrators set up Replay
schedules using an intuitive point-and-click interface. Replays can also be used to test new applications
and service packs on actual data without risk, efficiently support boot-from-SAN operations and
virtually eliminate backup windows on production systems.


Next up in our 8 Must Have series is #6, Thin Replication.

Compellent Pricing

This is the third of eight in a series titled 8 Must Haves for the IT Director

Number 3 – Thin Provisioning

Dell Compellent significantly reduces the cost of storage by enabling you to purchase and manage
fewer disk drives now and in the future. With other storage systems, physical disk capacity is
preallocated when the volume is created. Administrators estimate how much capacity may be required
for a given application and allocate “extra” space to accommodate growth. If the volume created is
500 GB, all 500 GB are set aside for that application. No other applications can use any of the preallocated
disk space, and none of it can be reclaimed later if actual utilization doesn’t coincide with
staff estimates. In most cases, only a fraction of the pre-allocated capacity is ever actually used,
resulting in the accumulation of purchased but “stranded” storage.

Such inefficient disk utilization inflates capital expenditures, operating expenditures and, ultimately,
your total cost of ownership (TCO). Administrators are forced to buy more capacity than needed
upfront, when the price per GB is sure to fall. Over time, as capacity is consumed (or stranded), even
more capacity must be purchased, further expanding the data center footprint. And all of this storage
must be provisioned manually, a time-consuming process that often requires downtime. In the end,
regardless of how much data is truly stored, all of these disks require continuous power and cooling.

Dell Compellent Thin Provisioning software, called Dynamic Capacity™, completely separates allocation
from utilization, eliminating preallocated but unused capacity. Administrators can provision any size
virtual volume upfront yet only consume physical capacity when data is actually written to disk. That
means you purchase the data you need to store your data today, then continue saving by expanding the
system on demand, adding the right capacity at the right time as your business needs change. In most
cases, organizations can regain 40 to 60 percent of disk space that would have been lost to preallocation.
You can even reclaim capacity from volumes provisioned with legacy systems using Thin
Import.

Next up in our 8 Must Have series is #4, Automated Tiered Storage.

Compellent Pricing