Non-standard RAID levels primer: RAID 5E and 5EE By Scott Lowe, Special to ZDNet Asia

By Scott Lowe, Special to ZDNet Asia
(This article was removed from the ZDNet Asia web site so I could not find the link. That’s why the references to diagrams have no associated diagram. If you ask, I will send you the newsletter email this came from.)
In my previous article on non-standard RAID levels, I talked a bit about RAID 1E, which is a RAID level that provides RAID-10-like functionality but with an odd number of disks. Although disks are pretty cheap these days, you never know when you might need to save a few bucks on a project!
In this article, I’ll provide a look at two other non-standard and closely related RAID levels — RAID 5E and RAID 5EE.
RAID 5E
With an E that stands for Enhanced, RAID 5E is a RAID 5 array with a hot spare drive that is actively used in the array operations. In a traditional RAID 5 configuration with a hot spare, the hot spare drive sits next to the array waiting for a drive to fail, at which point the hot spare is made available and the array rebuilds the data set with the new hardware. There are some advantages to this operational method:
You know for a fact that the drive that would have been used as a hot spare is in working order.
There is an additional drive included in the array, thus further distributing the array’s I/O load. More spindles equals better performance in most cases. RAID 5E can perform better than typical RAID 5.
There are a few disadvantages associated with RAID 5E as well:
There is not wide controller support for RAID 5E.
A hot spare drive cannot be shared between arrays.
Rebuilds can be slow.
The capacity of a RAID 5E array is exactly the same as the capacity of a RAID 5 array that contains a hot spare. In such a scenario, you would “lose” two disks’ worth of capacity — one disk’s worth for parity and another for the hot spare. Due to this fact, RAID 5E requires that you use a minimum of four drives, and up to eight or 16 drives can be supported in a single array, depending on the controller. The main difference between RAID 5 and RAID 5E is that the drive that would have been used as a hot spare in RAID 5 cannot be shared with another RAID 5 array; so that could affect the total amount of storage overhead if you have multiple RAID 5 arrays on your system. Figure A gives you a look at a RAID 5E array consisting of five drives. Take note that the “Empty” space in this figure is shown at the end of the array.
Figure A
A RAID 5E array with five drives
When a drive in a RAID 5E array fails, the data that was on the failed drive is rebuilt into the empty space at the end of the array, as shown in Figure B. When the failed drive is replaced, the array is once again expanded to return the array to the original state.
Figure B
A RAID 5E array that has been rebuilt into the hot spare space
RAID 5EE
RAID 5EE is very similar to RAID 5E with one key difference — the hot spare’s capacity is integrated into the stripe set. In contrast, under RAID 5E, all of the empty space is housed at the end of the array. As a result of interleaving empty space throughout the array, RAID 5EE enjoys a faster rebuild time than is possible under RAID 5E.
RAID 5EE has all of the same pros as RAID 5E but enjoys a faster rebuild time than either RAID 5 or RAID 5E. On the cons side, RAID 5EE has the same cons as RAID 5E, with the main negative point being that not a lot of controllers support the RAID level yet. I suspect that this will change over time, though.
As is the case with RAID 5E, RAID 5EE requires a minimum of four drives and supports up to eight or 16 drives in an array, depending on the controller. Figure C shows a sample of a RAID 5EE array with the hot spare space interleaved throughout the array.
Figure C
A RAID 5EE array with five drives
When a drive fails, as shown in Figure D, the empty slots are filled up with data from the failed drive.
Figure D
Summary In my previous article on RAID 1E, some readers mentioned that RAID 1E simply doesn’t seem like a good alternative to RAID 10, particularly since hard drives are so cheap these days. I happen to agree that there would need to be a seriously special case to consider RAID 1E. With regard to RAID 5E and RAID 5EE, however, I can see a very positive upside with regard to performance, especially for organizations that are already using or are considering RAID 5.

The True Cost of Printer Ink

Do you really get what you pay for when it comes to printer ink? We put the printer manufacturers’ claims to the test and tell you what you need to know about the cost of printing. here

The Continuing Chronicles of Shianne Els

In response to the letter to the Complaints Dept…
Hello complaints department of this newsletter…. I would like to make a formal complaint (do post this on the website as you see fit) that there has been NO mention of the two most GORGEOUS kids and their antics in FAR too long.!! I mean, Shianne has since discovered for herself that the singular of dishes is disha and Jaylen tells me I am a “good boy mummy” every time I go wee-wees in the toilet!
lv,
teal
Reply:
I must confess to not communicating one of Julie’s and my grandparent pleasure moments. Julie was attempting to teach Shianne how to spell and the correct pronunciation of a word. Julie said, “It’s dishes, d, i, s, h, e, s!” Shianne did not hesitate, she immediately retorted with absolute certainty, “No, it’s disha, t, q, r, s, v!”
Then there was the discussion about the bird droppings on our car. Shaianne noticed them and asked what they were. Julie told her about the birds not having toilets and sometimes they did their business while they were flying and the next question was priceless, “Do the birds go backwards before they go to the toilet?”
There’s a lot goes on in that four year old head!

Bulk Up to Lower Inflammation By Kelley Herring

You’ve likely heard quite a bit lately about a certain “miracle” substance. It’s proven to foster weight loss, improve gastrointestinal health, protect the heart, and even guard against cancer. Food manufacturers are boosting it in their products (and proudly displaying it on their labels). TV commercials featuring models exposing taut tummies urge you to whirl it into juice or water. And a recent book suggests that getting 35 grams every day is the key to losing weight and staying healthy for life.
What is this miracle substance? Fiber! Although devoid of calories, this non-nutritional vital nutrient is anything but lacking when it comes to your health. And new research shows yet another way roughage (as Mom calls it) can help prevent one of the major causes of chronic disease – inflammation.
A recent study published in the American Journal of Clinical Nutrition examined the relationship between C-reactive protein (CRP), a marker of inflammation and a predictor of heart disease and diabetes, with dietary fiber. The study evaluated the body composition, CRP, diet, and physical activity of 524 people. At the end of the study, CRP levels in the body were found to be inversely associated with the total fiber in the diet.
Bulk up on fiber to keep inflammation down. For maximum benefit, eat a variety of plant-based foods that provide both soluble and insoluble fiber. Here are a few:
Black beans, 1/2 cup: 7.5 grams of fiber
Chickpeas, 1/2 cup: 6.2 grams
Kidney beans, 1/2 cup: 5.8 grams
Navy beans, 1/2 cup: 5.8 grams
Northern beans, 1/2 cup: 5.6 grams
Pinto beans, 1/2 cup: 7.4 grams
Brussels sprouts, 1 cup: 6.4 grams
Apple: 5.7 grams
Pear: 5.1 grams
Whole wheat spaghetti, 1 cup: 6.3 grams
[Ed. Note: Kelley Herring is the founder and CEO of Healing Gourmet (www.healinggourmet.com), and is editor-in-chief of the Healing Gourmet book series. Learn more about how simple lifestyle choices can improve your health by reading ETR’s free natural health e-letter.]

Another New Tech Term: Lockers

As our music files grow to several thousands songs, where do we store them? You’re right! They’re called lockers. There are a few on line lockers now available to store your digital music files on-line, where you can download, sort and playback your music collection, automatically sync your locker and your local computer. You can also sync multiple computers with the same online locker so that all your computers can have the same synchronised music collection library. You can visit your grandma and still play back your favourite music collection online, as long as grandma has broadband of course.