Databases Reference
In-Depth Information
Contrast SMB with the use of an iSCSI network. iSCSI is a protocol used for accessing block data
over a server network. It requires the use of initiator software on the host server and a compatible
iSCSI storage target.
Both SMB and iSCSI utilize a server network to communicate. You must ensure that the server net-
work is low latency and has the bandwidth available to handle the demands that will be placed on it
by either technology. Most Fibre Channel networks are dedicated to handling only storage trafi c.
If you utilize a server network to transport block or i le SQL Server trafi c, it may need to be dedi-
cated to transferring only the storage trafi c. In lieu of dedicated networks, consider implementing
Quality of Service (QoS) that puts a higher priority on storage trafi c over normal network packets.
Keep in mind that no technology provides a magic bullet. Even robust networks can be i lled with
trafi c. Storage transfers are extremely sensitive to delay.
Shared Storage Arrays
Shared array controllers are primarily responsible for logically grouping disk drives. Sharing the
storage controller enables the creation of extremely large volumes that are protected against failure.
In addition to the normal features of direct attached storage controllers, a shared array controller
provides both storage performance and capacity.
Shared array controllers, often called SAN controllers, offer more advanced features than direct
attached systems. The feature sets are divided into three categories:
➤
Efi cient capacity utilization
➤
Storage tiering
➤
Data replication
Before diving into the features of SAN arrays, however, it would be helpful to look at some of the
language that storage administrators use to describe their systems.
Capacity Optimization
It has been our experience that most information technology professionals are not very good at
predicting the future. When asked how much performance and space they anticipate needing over
the next three to i ve years, administrators do their best to come up with an accurate answer, but
unfortunately real life often belies this estimate.
Meet Bob. Bob forecasted that his new OLTP application would start at 10GB and grow at 10GB
per year over the next i ve years. Just to be on the safe side, Bob asked for 100GB in direct-attached
storage. Bob's new widget sells like hotcakes and his database grows at 10GB per month. Seven
months in, Bob realizes that he is in trouble. He asks his storage administrators for another 500GB
in space to cover the next i ve years of growth.
Unfortunately, the storage and server administrators inform Bob that other users have consumed
all the space in his data center co-location. The information technology group is working diligently
to expand the space, but it will be six months before they can clear enough space to accommodate
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