| Tuesday 15th April 2008 |
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Found an interesting new web site Check out http://tomgrim.qassia.com/ |
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Google maps give close-up view of UN refugee camps Google technology first envisaged as a video game backdrop has been adapted to raise awareness -- and potentially financial support -- for the plight of refugees and vulnerable people once far from the public eye. more |
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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 |
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Australians want what’s bad for them: Biometrics Australians would prefer to use voice biometrics rather than PIN and password verification to prove their identity -- but security experts warn biometrics exposes consumers to even greater risk. more |
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Yahoo seeks AOL tie; Microsoft talks to News Corp Yahoo, which was widely believed to be running out of alternatives to accepting Microsoft’s takeover offer, has become a target of two warring camps of technology giants and their media allies, sources said on Wednesday. more |
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Malware writers now number one software makers For the first time, the amount of malicious software being released has outstripped that of legitimate software, according to new research. more |
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Microsoft issues five critical security patches As part of Patch Tuesday, the software giant releases security bulletins that address vulnerabilities in Windows, Microsoft Office, and IE. more |
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Couples turn to online espionage Research undertaken at Oxford University suggests that an increasing number of people are spying on their partners online. more |
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Ballmer envisions a new course for Microsoft Changes in the Internet, cloud computing, and open source are all having impacts on the way Microsoft does business, but not in the way many expect. more |
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Non-standard RAID levels primer: RAID 5E and 5EE 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. |
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Trim Down Windows to the Bare Essentials When you’re installing Windows in a virtual machine or on old, slow hardware, you want the leanest, meanest and fastest-running configuration possible. more |
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IBM motors toward racetrack memory Don’t make computers seek out data. Make the data move to where it can be used. That, roughly, is one way to describe the racetrack memory concept... more |
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Achieve a Deep, Uninterrupted Sleep 24 ways to get the rest you need. more |
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15 Ways to Maximize Your Lunch Hour Don’t let your break become an extension of your already overburdened day. more |
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Free Book MP3s This site allows free downloads of audio books. here |
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Accoustical Liberation of Books in the Public Domain LibriVox provides free audiobooks from the public domain. here |
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