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. )
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.
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.
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.
When a drive fails, the empty slots are filled up with data from the failed drive.
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.
This is an unprecedented admission by the U.S. government, which, until now, has clung to their statement that vaccines do not cause autism. Though they are still saying this, they have now conceded that the vaccines “significantly aggravated” an underlying disorder and caused autistic symptoms in at least one child.
It will be interesting to see how the other 4,900 cases waiting to be heard will turn out. No doubt many of these cases will report similar stories to Hannah Poling’s, where a healthy infant receives vaccinations and then suddenly becomes withdrawn and unable to communicate as they did before.
There is little doubt that thimerosal, a preservative that is 49.6 percent ethylmercury, is a contributing factor in many cases of autism. It is a well-established fact that exposure to mercury can cause immune, sensory, neurological, motor, and behavioral dysfunctions — all similar to traits defining, or associated with, autism.
There may also be another component in vaccines that is causing damage. For instance, according to Donald W. Miller, Jr., MD:
“Another important factor with regard to mercury on the mind … is synergistic toxicity — mercury’s enhanced effect when other poisons are present. A small dose of mercury that kills 1 in 100 rats and a dose of aluminum that will kill 1 in 100 rats, when combined have a striking effect: all the rats die.
Doses of mercury that have a 1 percent mortality will have a 100 percent mortality rate if some aluminum is there. Vaccines contain aluminum.”
Have Autism Rates Declined Since Thimerosal Was Removed From Vaccines?
Thimerosal was taken out of most childhood vaccines at the beginning of the decade. In 2006, studies of two government databases indicated that autism rates went up as thimerosal dosages increased, then began to decline as thimerosal was removed.
Yet, if you look at this Time magazine article, it says that autism rates have continued to climb since thimerosal was removed from vaccines in 2001. Why the discrepancy?
It could be due to the fact that in 2002 the U.S. government began recommending flu shots to children under 2 (and now recommends them for kids until they’re 18). Well, most flu shots still contain thimerosal, so many infants are still being exposed to mercury.
There is also the issue of vaccine timing.
“Giving too many vaccines over too short a time to infants whose nervous system is not yet fully developed can also trigger autism and its spectrum of disorders,” Dr. Miller says.
And, according to Dr. Russell Blaylock, multiple vaccines given close together over-stimulate your brain’s immune system and, via the mechanism of “bystander injury,” destroy brain cells.
What Else is Fueling the Autism Epidemic?
Autism now affects about one in 150 U.S. children. A small portion of these cases, perhaps 1 percent, may be due to genetic defects, and the rest are likely caused by exposure to toxic chemicals, viruses or other environmental influences.
One environmental influence that you may not have heard about was suggested by a November 2007 study in the Journal of the Australasian College of Nutritional & Environmental Medicine. It found that electromagnetic radiation (EMR) from cell phones, cell towers, Wi-Fi devices and other similar wireless technologies may be an accelerating factor in autism.
After five years of research on children with autism and other membrane sensitivity disorders, the researchers found that EMR negatively affects cell membranes, and allows heavy metal toxins, which are associated with autism, to build up in your body.
Meanwhile, autism rates have increased concurrently along with the proliferation of cell phones and wireless use.
EMR, the researchers say, could impact autism by facilitating early onset of symptoms or by trapping heavy metals inside of nerve cells, which could accelerate the onset of symptoms of heavy metal toxicity and hinder therapeutic clearance of the toxins.
If Your Child Has Autism …
There are several things you can do to help:
1. Have your child eat a diet tailored to their nutritional type. In my experience, nearly ALL children seem to respond favorably to the dietary changes when properly implemented.
2. Avoid giving your child pasteurized milk. This is imperative to the treatment of autism, and includes all milk products, such as ice cream, yogurt and whey. Even natural flavorings in food must be avoided unless the processor can guarantee, beyond a shadow of a doubt, that caseinate is not included. Anyone managing this illness without restricting milk is deceiving themselves.
3. Eliminating sugar, juice, soda, French fries and wheat (pasta, bagels, cereal, pretzels, etc) from your child’s diet is also highly recommended.
4. Make sure your child is getting proper sun exposure, as there is a link between rampant vitamin D deficiency and the proportionate jump in autism. The vitamin D receptor appears in a wide variety of brain tissue early in the fetal development, and activated vitamin D receptors increase nerve growth in your brain.
5. Use an effective intervention to address any emotional stresses your child faces as soon as possible. (Tom: Dianetics is the best.)
6. Homeopathy may also help ameliorate symptoms.