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Which Smart Array controllers support RAID ADG?

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Wesley W.D. Summers
Frequent Advisor

Which Smart Array controllers support RAID ADG?

In the Smart Array Configuration Utility Online Help, it describes "RAID ADG" (RAID Advanced Data Guarding).

This type of RAID-5 supports distributed parity, allowing for failure of up to 2 drives before the Logical drive ceases to function.

Unfortunately, my SA3200 doesn't seem to provide RAID ADG as an option, so I was wondering which Smart Array controllers do.

I guess that an Online Spare would provide a similar level of reliability, but a RAID ADG arrary WITH an Online Spare would seem to provide the best alternative of all the options.

If anyone can help by pointing me in the right direction to the relevant documentation, that would be MUCH APPRECIATED.


Regards, Wesley.
4 REPLIES
Prashant (I am Back)
Honored Contributor
Solution

Re: Which Smart Array controllers support RAID ADG?

Uwe Zessin
Honored Contributor

Re: Which Smart Array controllers support RAID ADG?

Wesley,
RAID-5 is striping with a single distributed parity. It allows only one disk drive failure.

RAID ADG is striping with double distributed parity. Both parity information (P and Q) are calculated using different mathematical algorithms, so they do allow any two disk drives to fail.
.
SAKET_5
Honored Contributor

Re: Which Smart Array controllers support RAID ADG?

Hi Wesley,

I would point you to the same links for documents as Prashant did. However, I would just like to comment on a few things:

1. Write performance would be decreased as for every write operations, two seperate parity blocks need to be generated instead of one in RAID 5.

2. Of the top of my head, RAID ADG is supported by default on Smart Array 6400 controllers, however on some controllers, you also have an option of purchasing an additional RAID ADG enabler module in terms of a software key or a hardware daughter board.

Hope this helps,

Please don't forget to assign the points ;)

Hope this helps.
Prashant (I am Back)
Honored Contributor

Re: Which Smart Array controllers support RAID ADG?

Hi,

Some Faqs that says RAID ADG is available with controller model SA-5304/128.

----------
Q: What is the difference between RAID ADG and RAID 5?
A: RAID ADG allows two drives to fail simultaneously without downtime or
data loss. (Data is also preserved if one drive fails and another simply has
a few bad sectors.) However, RAID 5 only allows one drive to fail. RAID
ADG thus provides a much higher level of fault tolerance than RAID 5.
Due to this higher level of protection, users can set up larger RAID
volumes, spanning up to 56 physical drives. With RAID 5, the maximum
recommended number of drives per volume is only 14.
RAID 5 and RAID ADG have equal performance when reading data, but
RAID ADG is slower when writing data due to the extra parity set that it
uses. The exact difference in performance will vary from one situation to
another.

Q: What products support RAID ADG?
A: RAID ADG is available with controller model SA-5304/128. It is also
supplied with the 128-MB cache module available as an option for the
SA-5302/32 and SA-5302/64 controllers.

Q: Does RAID ADG support online spares?
A: Yes. Customers can incorporate online spares for added data protection.

Q: How is RAID ADG activated?
A: Both a hardware key and a firmware upgrade are required. If the hardware
key (RAID ADG Enabler Module) is missing or faulty, the write cache is
disabled and the user cannot configure any further RAID ADG volumes.
Customers who buy SA-5304/128 controllers will be able to download the
firmware upgrade to activate RAID ADG from the Compaq website at


Regards,
Prashant S.
Nothing is impossible