NETWORK WORLD NEWSLETTER: MIKE KARP ON STORAGE IN THE ENTERPRISE
09/09/04
Today's focus:  Comparing SAS, SATA and Fibre Channel

Dear [EMAIL PROTECTED],

In this issue:

* Serial Attached SCSI vs. Fibre Channel and Serial ATA
* Links related to Storage in the Enterprise
* Featured reader resource
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Today's focus:  Comparing SAS, SATA and Fibre Channel

By Mike Karp

Today, we'll compare the new Serial Attached SCSI disk 
technology to other disk technologies now available.

For the next few years, Fibre Channel and Serial Attached SCSI 
(SAS) will continue to be the interfaces of choice on the SAN. 
Right now, the performance of the two is essentially the same 
(assuming Fibre Channel moves up to 4G bit/sec soon). Within 
about 18 months, though, SAS will likely double its speed, 
whereas the Fibre Channel community is still trying to decide 
whether the next step for the technology is going to be to 8G 
bit/sec or 10G bit/sec.

For the present, however, it is pretty much a toss-up as to 
which is better, Fibre Channel or SAS. Those who have Fibre 
Channel are likely to continue with it. But as parallel SCSI 
represents about 80% of the enterprise disk market, there is 
obviously plenty of opportunity for SAS.

But there is another contender to consider.

While SAS was being developed, vendors of the less expensive ATA 
drive technology were upgrading their offerings as well. Serial 
ATA (SATA) shares many characteristics with SAS and provides an 
inexpensive alternative for situations where investment in 
expensive drives is not warranted. We are very probably going to 
see lots of mixed SAS-SATA environments.

Major similarities between SAS and SATA are:

* Both types of drive plug into the SAS backplane. 
* The drives are interchangeable within a SAS drive bay module. 
* Both are long-proven technologies, with worldwide acceptance.

Major differences between the two technologies are:

* SATA devices will be less expensive. 
* SATA devices use the ATA command set. 
* SAS drives have dual porting capability, faster spindle speeds 
��and lower latencies. 
* While both types of drives plug into the SAS backplane, a SATA 
��backplane cannot accommodate SAS drives. 
* SAS drives are tested against much more rigid specifications 
��than are SATA drives, and have a significantly longer mean time 
��between failures and duty cycle. 
* SAS drives are faster, and offer several features not 
��available on SATA, including variable sector sizes, LED 
��indicators, dual ports and data integrity.

So what is the best choice for you?

The choice between Fibre Channel and SAS is at present a tough 
one, as performance is going to be pretty much the same on both 
platforms for the near future. If you are a happy Fibre Channel 
user, and don't mind paying the slight price differential, you 
are likely to continue using it.

If you are looking for more flexibility however, then the 
SAS-SATA interchangeability is likely to be more appealing. The 
appeal of this will increase if the idea of tiered storage has 
value for you (if you are considering the benefits of 
information lifecycle management, this should be the case).

As for SAS and SATA, when choosing between them follow this 
rule:

Choose SATA when cost is the most important issue; choose SAS 
whenever data availability and performance count. If you buy a 
SAS box to put them in, you can play mix-and-match with SAS and 
SATA drives to your heart's content.

For the long run, as I gaze into my crystal fishbowl, here is 
what I see:

1. On the desktop, SATA (that was easy). 
2. For servers, both direct-attach and inside-the-box drives 
   will be SAS. 
3. For near-line storage, "best in class" will lose out to "good 
   enough." SATA wins. 
4. For connectivity to SANs, Fibre Channel will continue to 
   lead, but iSCSI will pick up momentum. 
5. For disk drives on the SAN, SAS will likely win, but the SAN 
   connection will continue to be Fibre where it is presently 
   Fibre.

Unless Fibre Channel comes out with a low-cost alternative to 
its present set of drives, it is likely to lose out as a drive 
connection in the long run.
_______________________________________________________________
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:[EMAIL PROTECTED]>.
_______________________________________________________________
This newsletter is sponsored by Intel 
A NW Special Report: 
The State of Wireless LANs  

Wireless has becomes more integrated and accepted as a way of 
doing business. However, several questions are raised about its 
current state; what are the trends and best practices for 
deploying wireless LANs?  What are the leading applications? 
What are the tradeoffs in current wireless standards?  What are 
the best options for wireless infrastructures and security 
mechanisms?  Click here to download your copy, no registration 
required http://www.fattail.com/redir/redirect.asp?CID=79110
_______________________________________________________________
ARCHIVE LINKS

Archive of the Storage newsletter:  
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Breaking storage news and analysis:
http://www.nwfusion.com/topics/storage.html
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