The Internet, e-commerce, and e-services significantly affect
traditional applications. In the past, these applications were
categorized by performance (number of I/O per second) and throughput
(megabytes per second). A third parameter, referred to as "Quality
of Service", becomes essential. It relates to the application's
availability, or its ability to deliver the necessary bandwidth
under extreme load conditions and under failure conditions. .Figures
2 and 3 identify typical performance and throughput for four applications,
showing OLTP applications with the highest demand for low latency
I/O performance and the smallest amount of actual data throughput.
Decision support requires the
highest bandwidth for searching through terabytes of data. The
Multimedia and image processing applications require the ability
move massive amounts of image data to people working on the many
various stages of image processing. Video servers have unique
requirements in that they need high volumes of data to provide
continuous data streams to thousands of customers and these must
be uninterrupted data streams in order to provide the real time
images that are being viewed. As far as availability is concerned,
OLTP applications require the highest degree of availability,
followed by decision support, multimedia, and file server applications.
The emergence of cost-effective digital data, images, sound, and
video and the ease with which we can use, analyze, and manipulate
this data--then deliver it through new broadband communications
technologies--introduce new storage considerations for traditional
applications. Corporations now require much larger storage systems
to contain current data, never mind historical data. Decision-makers,
in turn, continually access and analyze the stored data for new
information and insights into improving productivity and delivering
new services.
All this data still requires storage for backup, archiving, data
replication, remote vaulting, and data sharing. New developments
in storage help alleviate the demands brought on by the Internet,
e-commerce, and e-services.
Backup and Archiving
The Internet has forced businesses
everywhere into 24 x 7 operation, 365 days per year. Continuous
database and application availability is mandatory, leaving no
time for a backup window. Meanwhile, the volume of data to back
up is growing, and backups are more important than ever.
As a result, backup (along with data replication, mirroring, and
remote vaulting) is evolving in several directions:
· Realtime backup or window-less backup (also called hot backup) essentially lets you back up a volume or file periodically and automatically without affecting normal system operations. Recently introduced backup products can successfully back up changed records or bytes instead of backing up complete files.
· LAN-less backup lets you perform backup through a special high-speed dedicated network, usually a SAN, connecting storage systems and servers. Data moves from the disk to the server, which retransmits it through the SAN to a SAN-connected library. Data is transmitted at much higher speeds and LANs are freed from this data-intensive load.
· Server-less backup
moves data directly from disk to tape through the SAN fabric without
further involving the server or the LAN. This frees up the CPU
and LAN resources from the backup overhead. Even though you have
offloaded the host what you need to look at is the amount of I/O
bandwidth in your storage subsystems. Lets say your storage system
that can provide 140MB/sec. If your data warehouse requires 120MB/
and your backup application is requires 100MB/sec then the two
applications would require 220MB/sec. The subsystem would be
about 100MB/sec short and the two applications would be effected.
This would mean that your backups or queries do not complete in
their allotted time. Leaving the IS dept in the position of not
having backups going into the next day or not having data from
queries when required, SAN backup moves the potential bottleneck
from the LAN or the CPU out to the storage subsystems. Your capacity
planning now needs to focus more on the SAN and storage bandwidth.
· Remote backup backs up data to a remote site.
The connectivity distances that Fibre Channel allows make it easier
to deploy remote sites for business continuance and disaster recovery
purposes. Because of this capability, use of remote backup is
likely to increase.
Resource and Data Sharing
As more users need to access and analyze stored data, sharing that data among users and different platforms becomes important. As a result, storage systems that support sharing data and resources in a heterogeneous environment are evolving at four levels of sophistication:
· Resource sharing--A storage subsystem attached to multiple computer platforms is divided into partitions, each partition being accessible only to its owning platform or to a certain number of homogeneous platforms. Such sharing lets users share data and administrators consolidate backups--from many different servers to locally attached tape drives--into one tape library.
· Dynamic resource sharing--All storage is available to any connected host; hosts are allocated storage as they need it. If one host needs the storage, it can use any or all of the available space. If a host deletes a file, that space is available to any other host. Retrieve is among the vendors that pioneered this implementation]
· Data copy sharing--This approach involves replication of the data. Data is the same across copies at the time of copy creation, but the copies can change independently afterward. There is no assurance that the copies will remain identical.
· True data sharing--Data
is shared without making a copy, and multiple computer platforms
can access the same physical instance of the recorded data on
a storage subsystem. In the highest level of true data sharing,
called "concurrent data sharing," all platforms can
either read or update the data at the same time.
By: Farid Neema
PERIPHERAL CONCEPTS, INC.
351 Hitchcock Way, Suite #B-200
Santa Barbara, California, 93105
Tel: (805) 563-9491
fneema@silcom.com
This article was published in the Marh issue of Windows2000 Magazine