Hands-On Testing and Analysis

All About Data Protection Part IV – RAID6 – Double The Parity, Double The Fun

Belt And Suspenders

In today’s episode our hero, always searching for ever higher levels of resiliency, adds a second parity strip, sticks a feather in his cap and calls it RAID6. RAID5 systems protect user data against a single device failure, but leave data vulnerable to multiple device failures and more significantly read failures from otherwise working drives during a rebuild. RAID6 technologies …

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The Data Protection Diaries Part 3 – Parity RAID

Raid 3

In this installment of As the Disk Drive Turns, we’ll explore RAID levels two through five and the math(s) they use to protect data with less overhead than mirroring. RAID2 and RAID3 Bits and Bytes Not Blocks RAID2 stripes data across multiple drives at the bit level using Hamming codes. RAID3 uses parity but at the byte, not block level. …

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All About Data Protection Part 2¾ – A Few Words On Parity


Unfortunately, parity is one of those words that means different things depending on the context. To make things worse we IT folks talk about double-parity, a concept that would make our favorite mathematician, Rachel Traylor Ph.D., blow her top. Strictly speaking, parity is the special case of a forward error correction code, which adds one error check bit to some …

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All About Data Protection – Part 2 How RAID Works, Stripes and Mirrors


Here’s how storage systems use the concepts of RAID to protect your data. In A Case for Redundant Arrays of Inexpensive Disks, Patterson, Gibson and Katz propose five methods for using arrays of slow, unreliable but inexpensive drives to match the performance and reliability of the SLEDs (Single Large Expensive Disks) then dominating the minicomputer and mainframe storage market. They …

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All About Data Protection – Part One Where Did RAID Come From?


Just about all modern data protection schemes divide data into some arbitrarily sized block. Then, they either duplicate that block across multiple storage devices, or store portions of that data block, which we’ll call strips, in stripes across multiple storage devices, with one or more additional strips in each stripe containing parity or other erasure code data. Those are pretty …

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Notes from the NAND Front


I ran across an interesting article on the site about the state of the NAND flash market. While much of the article covers trends I wrote about in a post at SearchSolidStateStorage like the difficulty vendors have had in ramping up 3D NAND production there were a few tidbits I thought you, my dear readers, would be interested in. The first …

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Update to Flashstack/Nutanix


We’ve updated the cost of acquisition report we did for Pure comparing the Pure/Cisco FlashStack converged infrastructure to a hybrid Nutanix cluster. We misread the Nutanix spec sheet and used the power consumption of a 4-node Nutanix block as the consumption for a single node.  This lead us to believe the FlashStack solution used less power when in truth the …

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Disagreeing without being Disagreeable

Any one that knows DeepStorage knows that we’re opinionated and that we’re always willing to have a reasonable debate about our opinions. Unfortunately, as we’ve discovered in politics recently, some people take anything you say about them that isn’t a straight up compliment as an attack that must be responded to with as much force as possible. Again, as in …

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HCI and Data Locality

Locality 2 E1500393165607

While I rarely apply quantum mechanics in my day to day life studying quantum mechanics taught me an important life lesson; things in the real world sometimes operate in ways counter to our intuitive understanding. Unlike the Mandelbrot set and other fractals which look the same no matter how deeply you examine them many things and ideas in the real …

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Stormagic Sticks to the HCI Sweet Spot

I’ve long believed that HCI was the best solution for the “small-scale” systems in remote and branch offices and SMEs. In many cases, these sites have just a handful of workloads that could easily be handled by a single modern server. A pair of servers with a decent VSA sharing out their local storage devices provides plenty of capacity, horsepower, and …

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