Storage Basics – Part IX: Alternate IOPS Formula

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It's been a long time since I published an article in my Storage Basics series - the series has been some of the top content on my site to date.  I sat for a beta version of the VMware Certified Advanced Professional - Desktop Design (VCAP-DTD) test today and was reminded by the test of a post I had in waiting about an alternate way to calculate IOPS (hint hint - memorize these formulas).  I have several more articles sitting in draft form, but a new job, crazy kids, home improvement projects, and a wife with chronic cerebral spinal fluid (CSF) leaks (it sounds bad - and it is - but look on … [Read more...]

Storage Basics – Part VIII – The Difference in Consumer vs. Enterprise Class Disks and Storage Arrays; or ‘Why is the SAN you are proposing so darn expensive?’

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As both an IT Manager and storage & virtualization consultant, I have shepherded SMB's through SAN purchases in support of VMware environments.  This may not hold true for the bigger IT shops, but as I take these smaller companies through the SAN purchase process, a common set of questions is often asked - Do we really need a SAN, and why is it so darn expensive!?!? I quickly learned that my (cheeky) answer "because it's enterprise class, baby" just didn't cut it.  So how do you move beyond "I can get a 2TB hard drive for $100 at Best Buy, why are you selling me on 300GB hard drives for … [Read more...]

Storage Basics – Part VII: Storage Alignment

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At the risk of beating a dead horse, it's time to resurrect my Storage Basics series.  I've recently had some great feedback on the series and figured I should round out a few of the concepts before I wrap it up.  I want to cover a topic often discussed amongst virtualization professionals, but one I often find general practitioners and server admins not understanding: storage alignment.  Storage alignment, or the lack of alignment, is not a new issue and is not unique to VMware or virtualization in general.  However, the effects of misaligned storage can be more greatly felt in terms of … [Read more...]

Storage Basics – Part VI: Storage Workload Characterization

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Most of what I covered in Storage Basics Parts 1 through 5 was at a very elementary level.  The math I used to do IOPS calculations, for example, is only true under very certain conditions.  RAID controllers implement caching and other techniques that skew the simple math that I provided.  I mentioned that the type of interface that you ought to use on your storage array should not be randomly chosen.  In fact, choosing the right array with the appropriate components and characteristics can only be done when you enlighten your decision with a characterization of workloads it will be … [Read more...]

Storage Basics – Part V: Controllers, Cache and Coalescing

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My Storage Basics series has been neglected for some time (sick kids, snow storms, VMware Upgrades, SAN implementations and some Cisco switch upgrades took all my free time), so let's jump right in to Part V - Cache, Controllers, and Coalescing.   Between the alliteration and fancy words, it might seem like I am about to tell a tale of international espionage.  Unfortunately, my introductory treatment of these aspects of a storage system will probably not keep you on the edge of your seat - but I'll try to keep it interesting. Throughout this series, we've been working our way from the … [Read more...]

Storage Basics – Part IV: Interface

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In parts I, II, and III of the Storage Basics series we looked at the basic building blocks of modern storage systems: hard disk drives.  Specifically, we looked at the performance characteristics of disks in terms of IOPS and the impact of combining disks into RAID sets to improve performance and resiliency.  Today we will have a quick look at another piece of the puzzle that impacts storage performance: the interface.  The interface, for lack of a better term, can describe several things in a storage conversation.   It can be let me break it down for you (remember, we're keeping it simple … [Read more...]

Storage Basics – Part III: RAID

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This is the third in a multi-part series on storage basics.  I've had some good feedback from folks in the SMB space saying that the first couple posts in this series have been beneficial, so we'll be sticking with some basic concepts for another post or two before we dive into some nitty-gritty details and practical applications of these concepts in a VMware environment.  In the second post of this series I introduced the concept of IOPS and explained how the physical characteristics of a hard disk drive determine the theoretical IOPS capability of a disk.  I then noted that you can aggregate … [Read more...]

Storage Basics – Part II: IOPS

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In Part I of this series, I discussed the important of storage performance in a virtual environment (really any environment, virtual or not, where you want acceptable performance), and introduced some of the basic measures of a storage environment.  In Part II, we will look more closely at what may be the most important storage design consideration in a VMware server-consolidation enviornments, many SQL environments, and VDI environments to name a few: IOPS. If we stick with a single-disk-centric approach as we did in Part I, IOPS is quite simply a measure of how many read and write … [Read more...]