The Storage Rack: Low-Power Alternatives Exist to Solve Storage Needs

CHANNELS

ON THE WEB

PRINT EDITION

BZ MEDIA

AS OF 8/20/2008 9:43AM EST

The Storage Rack: Low-Power Alternatives Exist to Solve Storage Needs
By Mike Karp

June 15, 2008 —

“Storage density” is the term that describes how much storage capacity can be packed into a specified amount of space. The actual measurement varies a bit depending on your focus. Disk-drive vendors measure bits per square inch, while tape vendors think in terms of bits per linear inch. Data center managers measure things at a more macro level; for them storage density is a measure of terabytes (and increasingly, petabytes) per square foot of floor space.

At least that’s the way they did things until about a year ago.

Those of you who do not walk to work may have noticed that gas prices have been inching up of late. If the monthly power or heating bill at home comes out of your account, you are acutely aware that prices are going up. And if the price for data center power and cooling is a line item in your budget, then you really feel the pain.

Actually, the price of power is just part of the problem. On the other side of the coin, many data centers have simply maxed out their ability to draw power from the local power grid. They may be willing to pay for more power, but, in some locations, there just isn’t any more power available at any price. At such places, vendors know that if they have any hope of replacing existing storage assets they’ll have to do so without adding to the existing power load. The mantra in this case has become “more storage, less power.”

If power consumption is high on your list of worries, it’s time to consider a newer metric for storage density: gigabytes per watt, a measurement that indicates how much storage you get from each watt of electricity you buy. Fortunately, there are several ways to squeeze more gigabytes of storage from each watt of power consumed in the data center. You’ll have to choose wisely though.

Massive arrays of idle disks systems spin down their disks until the data on them is needed, at which point they spin up again for as long as they are in use. This is highly efficient in terms of power use, but is clearly not a suitable technology when high performance is needed. Use it for “persistent” data, information that needs to be available for reference but for which speedy access is not necessary. Think online archives.

At the component level, a new generation of small form factor disks will arrive toward the end of this year—samples are already out there—from all the major vendors. These 2.5-inch HDDs will offer high performance (at both 10K and 15K spindle speeds) and much lower power consumption, which means needing more of them to achieve a targeted capacity than would be the case with the larger SATA drives, because they take up less space and need less power the “physical density” accommodates the need for “power density.” When I was giving the Serial Attached SCSI keynote talk for the SCSI Trade Association last month, interest in these was hot. These are for tier-1 storage devices to be used with your most important data.

Want even less power consumption? Don’t use spinning disks at all. Solid-state devices (SSDs) have become interesting of late because their prices are now beginning to rival those of traditional top-tier disk arrays. Because they have no spinning media, they consume less power than more traditional approaches, and because they move data across RAM with no mechanical movement, I/O speeds are measured in microseconds rather than milliseconds.

While the pricing has dropped significantly of late, they are still more expensive than HDD-based arrays, and so are generally suitable only for specialized situations. This doesn’t mean high-performance computing, such as engineering applications, however. Rather, it indicates a need for judicious use of a relatively expensive asset. Plain old commercial databases can get lots of value from these when they are used intelligently, which is to say when sites put metadata rather than data on them. SSDs represent what may come to be thought of as a new storage tier, “tier 0.” Storage administrators should talk with their database administrators about this.

Finally, you have the alternative of just doing it in software. Every vendor now offers data de-duplication capability (sometimes referred to as “single instancing”), which eliminates redundant data and reduces the overall need for storage capacity by anywhere from 10 percent to 30 percent. Note that there are several approaches to de-duping, and the numbers the vendors give you are frequently highly optimistic. Note, also, that some data does not de-dupe well (it’s hard to identify redundant bytes in a graphics file), and that de-duping becomes increasingly efficient as more data is kept online for comparisons. De-duping is an easy way to save lots on storage costs without having to commit to new architectures.

Storage as a function of power appears to be a simple measurement of efficiency, but experienced readers will realize it is not as simple as it appears to be. It makes no more sense to measure the efficiency characteristics of tier-1 storage against archiving devices than it does to compare a Ferrari with the family station wagon. Just as the Ferrari won’t cut the mustard when it is time to take the trash to the dump, some technologies will be unsuitable for your needs. But at least you have lots to choose from.

Mike Karp, senior analyst with Enterprise Management Associates, can be contacted at mkarp@enterprisemanagement.com.

Related Search Term(s): Power, storage hardware

EMAIL THIS ARTICLE

SEND FEEDBACK

MORE COLUMNS

SUBSCRIBE TODAY!
Systems Management Week

PDF & PRINT EDITION

Download Current Issue!
ISSUE 8/15/2008 PDF

Need Back Issues?
DOWNLOAD HERE

Receive The Print Edition?
SUBSCRIBE HERE

GET NOTIFIED!
About all of the latest Resources

HOME SITE MAP RSS CURRENT ISSUE BACK ISSUES SUBSCRIBER SERVICES ABOUT US CONTACT US BZ MEDIA