All about RAID

NETWORK WORLD NEWSLETTER: MIKE KARP ON STORAGE IN THE ENTERPRISE
07/07/05
Today's focus: All about RAID

Dear networking.world@gmail.com,

In this issue:

* On a level with RAID
* Links related to Storage in the Enterprise
* Featured reader resource
_______________________________________________________________
New IT event exclusively for small to mid-sized businesses
coming to New York on July 19

At IT Strategies for Small to Mid-sized Businesses: A Practical
Blueprint for Smart Growth, you'll learn how to identify the
technology that will add value to your company. How to invest in
it early enough and at the right level. And how to deploy it
effectively. Attend this special Network World event in New York.
Click for all the details:
http://www.networkworld.com/SMBS5NLNY1
_______________________________________________________________
This newsletter is sponsored by Nokia
Empower Your Mobile Enterprise

Nokia believes that business mobility will fundamentally change
the way work gets done-and for the better. To allow the entire
organization to get the most from this paradigm shift in
productivity, Nokia Enterprise Solutions focuses on delivering
increased efficiency through enhanced mobility. Learn more by
downloading this white paper today!
http://www.fattail.com/redir/redirect.asp?CID=107730
_______________________________________________________________
FREE NETWORK WORLD PRINT SUBSCRIPTIONS FOR NETWORK WORLD
e-NEWSLETTER SUBSCRIBERS

SUBSCRIBE TODAY - Receive 51 complimentary issues of Network
World Magazine. Network World delivers an extensive line-up of
product, service and industry news, comparative product reviews,
product tests, technology insiders, expert opinion and
management advice.
http://www.fattail.com/redir/redirect.asp?CID=107488
_______________________________________________________________

Today's focus: All about RAID

By Mike Karp

RAID in its several forms provides the backbone for most of our
high availability, high performance storage. RAID devices have
been with us since the late-1980s, and by now are so much a part
of our IT lives that many folks have even forgotten what the
acronym stands for.

Actually there have been several meanings for RAID over the
years. The most frequently used has been Redundant Array of
Independent Disks, but the "I" has also stood (often,
inaccurately) for "inexpensive," and the "D" has on occasion
meant "devices" (useful when describing that relative rarity,
tape arrays).

Many levels of RAID have been defined over the years, and most
have been implemented at one time or another. Most prominent
among these have been:

* RAID 0, which stripes data across its disks to provide faster
  access but provides no added protection.
* RAID 1, which duplicates data via mirroring to provide fault
  tolerance.
* RAID 3, which offers speedier reads by striping data across
  the drives and then accessing the drives in parallel. This
  offers fault tolerance because it stores parity bits on a
  separate, dedicated disk drive.
* RAID 5, which stripes both data and parity across all drives
  to get better load balancing. This in turn provides better
  transfer speeds on reads along with increased data protection.

All of these RAID levels were defined by an industry
organization, the RAID Advisory Board.

There have been other RAID implementations as well. RAID Levels
2 and 4 were defined by the RAID community, but were rarely used
and have been seen about as often as Bill Gates at Linux World.
(Trivia question of the week: Name the Massachusetts-based
company that had the only commercial implementation of RAID 2,
which used bit-striping for speed.) Additionally, combinations
of RAID Levels 1 and 0 (usually written 1+0) and of Levels 0 and
1 (usually written 0+1) have also been popular. 1+0 is mirrored
striping and 0+1 is striped mirroring (despite being
combinations of the same levels, they are not the same thing).

Two other presumed forms of RAID, Levels 6 and 7, were
proprietary solutions pushed by some vendors, and while in some
cases they were technologically successful, they failed in the
marketplace due to the essentially proprietary nature of their
solutions.

RAID 7 was wholly proprietary to Storage Computer, a New
Hampshire-based firm, which today is a shell of its former self.

RAID 6 looks a lot like RAID 5, except that parity is written to
two drives rather than one. Because RAID 6 performs two
different parity computations rather than one, it provides
increased fault handling and can tolerate two concurrent device
failures where the other RAID levels only support a single
failure.

The extra calculating and writing to a second parity disk means
that write operations for Level 6 are slower that for Level 5,
but RAID 6 has not succeeded in the marketplace because it has
no industry standard to which it can conform. This of course
means that every implementation until now has been proprietary.

Now a number of industry players are banding together to
standardize RAID 6, and there is some likelihood that it may
actually become a proposed industry standard by year-end. If
this actually happens - Intel is supporting this movement, so it
may become a standard - RAID 6 may well become the RAID level of
choice for read-intensive applications such as video-on-demand
and other fixed content implementations. The industry players
involved include: Adaptec, Fujitsu, HP, IBM, Intel, LSI Logic
and Promise Technology.
_______________________________________________________________
To contact: Mike Karp

Mike Karp is senior analyst with Enterprise Management
Associates, focusing on storage, storage management and the
methodology that brings these issues into the marketplace. He
has spent more than 20 years in storage, systems management and
telecommunications. Mike can be reached via e-mail
<mailto:mkarp@enterprisemanagement.com>.
_______________________________________________________________
This newsletter is sponsored by Nokia
Empower Your Mobile Enterprise

Nokia believes that business mobility will fundamentally change
the way work gets done-and for the better. To allow the entire
organization to get the most from this paradigm shift in
productivity, Nokia Enterprise Solutions focuses on delivering
increased efficiency through enhanced mobility. Learn more by
downloading this white paper today!
http://www.fattail.com/redir/redirect.asp?CID=107729
_______________________________________________________________
ARCHIVE LINKS

Archive of the Storage newsletter:
http://www.networkworld.com/newsletters/stor/index.html

Breaking storage news and analysis:
http://www.networkworld.com/topics/storage.html
_______________________________________________________________
Why is a virtual infrastructure so important? Webcast explains.

Enterprises of all sizes are using virtual infrastructure to
increase the efficiency and cost-effectiveness of their IT
operations. Learn the benefits and trends of virtualization and
how IT departments are effectively using this software.
http://www.fattail.com/redir/redirect.asp?CID=107617
_______________________________________________________________
FEATURED READER RESOURCE
TEN WAYS TO STOP SPYWARE

You will get spam down to a manageable level this year, but then
spyware will kick in. Spyware cleaners will help, but won't
eradicate all the unwanted activity at the office, at home.
Here's a ten step guide you can follow to curb the spyware
problem:
<http://www.networkworld.com/nlstorage3040>
_______________________________________________________________
May We Send You a Free Print Subscription?
You've got the technology snapshot of your choice delivered
at your fingertips each day. Now, extend your knowledge by
receiving 51 FREE issues to our print publication. Apply
today at http://www.subscribenw.com/nl2

International subscribers click here :
http://nww1.com/go/circ_promo.html
_______________________________________________________________
SUBSCRIPTION SERVICES

To subscribe or unsubscribe to any Network World e-mail
newsletters, go to:
<http://www.nwwsubscribe.com/Changes.aspx>

To change your e-mail address, go to:
<http://www.nwwsubscribe.com/ChangeMail.aspx>

Subscription questions? Contact Customer Service by replying to
this message.

This message was sent to: networking.world@gmail.com
Please use this address when modifying your subscription.
_______________________________________________________________

Have editorial comments? Write Jeff Caruso, Newsletter Editor,
at: <mailto:jcaruso@nww.com>

Inquiries to: NL Customer Service, Network World, Inc., 118
Turnpike Road, Southborough, MA 01772

For advertising information, write Kevin Normandeau, V.P. of
Online Development, at: <mailto:sponsorships@nwfusion.com>

Copyright Network World, Inc., 2005