Ode to the Disk Array

by Steve Todd | January 19, 2010

  • My Vault
We’ve been discussing a simple diagram which emphasizes, at a very high level, that one of the core technologies within the high-tech information industry is the persistent storage of the digital bits that are being generated by applications. Persistent storage can take many forms, including CD-ROM, tape drives, solid state drives, USB flash drives, and of course the old favorite, hard disks. Hard disks are also called hard disk drives (HDDs) or head-disk-assemblies (HDAs).

hard disk manufacturing; Seagate plantWhen interviewing for a position at a high-tech firm, knowledge of these technologies will definitely be to your advantage. The persistent storage of the world’s information is a hot field. There are many uses for CD-ROMs, tape drives, solid state drives, USB flash drives, and other types of peripheral storage devices. You can study their features and functions, and you can learn about the customer situations in which they are likely be used.

From my biased point of view, I view these storage devices as secondary when compared with the widespread deployment of hard disk drives. They can be found in the majority of desktop computers and laptop devices. They are packaged in rectangular canisters that contain platters that spin, arms that seek, and heads that read and write magnetic bits of information.

You may get a job at a high-tech corporation that builds hard drives, such as Seagate or Western Digital. These companies are always searching for innovative ways to reduce costs, increase capacity, and reduce power consumption.Perhaps the most significant high-tech innovation in the last two decades, however, is the introduction and evolution of the disk array, which is essentially a cabinet full of disk drives (the previous Wikipedia link depicts two disk arrays manufactured by my company, EMC). Every large, Fortune 500 company will buy their hard drive technology from a disk array vendor or vendors (as opposed to buying individual disk drives). Even small-to-medium size businesses prefer to purchase disk arrays.

Familiarize yourself with disk array features and functions. They are a critical aspect of a corporate data center. In future posts I plan on elaborating more specifically about their many capabilities. In this post, however, I want to take a high-level look at their usefulness. Here are some of the more important features of a disk array:

  • They are usually scalable. A small business can buy a disk array that contains as few as five hard drives, and they can add dozens more as their business grows.
  • They centralize the management of user storage. Instead of storing customer data on personal hard drives, business will store the information on a central disk array. A system administrator can centrally allocate and dedicate storage to specific users.
  • They centralize administrative tasks such as backups. Backup software can focus on backing up the entire disk array, as opposed to backing up individual hard drives.
  • They can handle more traffic than individual hard drives. A disk array will often aggregate multiple hard drives together and make them appear as one, large disk drive. This “virtual disk” can actually handle simultaneous requests in parallel.
  • They can be shared among many servers. An individual disk drive is typically dedicated to one server. A disk array can carve up disk capacity and dole it out to multiple servers.
  • They protect data better than individual hard drives. Should a hard drive fail inside of a disk array, the disk array will typically have a variety of recovery algorithms that allows the user to ride through a hard drive failure transparently.

The disk array business is a multi-billion dollar enterprise. As the world’s footprint for information data continues to grow, the corporations that engineer and build disk arrays will continue to thrive and hire. If you interview with a disk array vendor (or if you interview at a company that purchases equipment from a disk array vendor), ask them about their disk array technology choices.

In future posts, I will provide a set of questions that makes it clear that you have a working knowledge of disk array technology.

Steve
http://stevetodd.typepad.com
Twitter: @SteveTodd
EMC Intrapreneur

Filed Under: Technology

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