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Recent Posts by Andrew Binstock
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Solid state drives (or SSDs) are an emerging storage technology that has been getting increasing press over the last year due to its availability as an option for laptops and, in certain segments, for IT sites. Many claims have been made on behalf of SSDs, including that they are faster and greener and that, as such, they represent the future of disk storage. In this column, I look at how the technology works and why they're not greener nor a widespread alternative to hard disk drives.
Before diving into the topic, it's important to be clear what I am referring to as SSDs, as the term is already in the process of corruption. I am referring to drives made up of flash memory, not the DRAM disk products that have been around for decades for sites that need high-speed disk I/O.
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In June and August of last year, I wrote a pair of columns in which I extolled the value of virtualization as a solution to excessive energy consumption. The primary benefit, as I described it, is that virtualization makes it possible to consolidate multiple applications onto a single server. That is, apps that currently run on dedicated systems can be moved en masse to a single server that consumes less power -- generally, far less power -- than that required by the dedicated servers.
This economy derives from two principal factors:
1) Modern servers are much more energy-efficient than their forbears. This is true in absolute terms and relative terms. In fact, in relative terms, such as watts per mips, today's systems are orders of magnitude more efficient.
2)
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Until very recently, the need for IT to really include eco-concerns as part of overall strategy did not have universal appeal. Surely, sites located in areas such as southern Manhattan where power distribution is already running at maximum capacity have a grave problem. And likewise sites that need more room but have tight expansion constraints. For them, green has been a key preoccupation for a while.
For most other IT sites, however, the main driver for green has been cost reduction -- and until the last few months, the cost of energy was tolerable even if somewhat higher than budgeted. So, pressure existed to reduce unnecessary consumption, but not place the issue at the center of IT concerns. However, with oil now regularly surpassing $130 per barrel, there is no longer any
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The golf expression "It's the rub of the green" means the equivalent of "them's the breaks." It refers to the fact that you're going to have your share of good luck and bad luck when your ball is on the green. Every so often you'll hit a divot or other irregularity -- and sometimes the results will be good, other times not so much. It's the rub of the green. Today, I want to refer to the expression in a rather different sense: when green rubs people and IT the wrong way. The world today is so prone to over-marketing, so accustomed to rapid cycles of surging popularity followed by a precipitous descent into oblivion that, at times it feels like the only sane way to deal with new trends is to tune them out. This applies even to green. Let's not forget that the
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As reported in the March 26th issue of GreenerComputing News (you do subscribe, right?), the Standard Performance Evaluation Corp. (SPEC) is in the process of formulating a power-consumption benchmark for workstations. SPEC is a vendor-neutral, non-profit organization that designs benchmarks for the computer industry. It also hosts a website, www.spec.org, that presents benchmark results for various platforms. Those results are provided by vendors of hardware and software systems who certify that they ran the benchmarks in accordance with SPEC guidelines. While SPEC cannot and does not vouch for those results, the industry puts real effort into maintaining the integrity of posted results. And because those results often figure
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The hard-disk drive (HDD) is the most important, mostly mechanical component in regular use on computer systems. Due to their highly mechanical nature, it is easy to believe that disks consume the most amount of power, especially when thrashing (that is, rapidly moving the heads to various locations -- a process that generates an easily recognized sound).
This is easy to believe, but incorrect. Rarely do HDDs consume more power than the processor. The disk industry has been remarkably effective over the years at keeping power consumption low.
A typical mid-range HDD today uses somewhat under 10 watts. Actual consumption depends on the type of drive, capacity and usage. Let's first look at how to measure consumption for this one component, and then see what the figures tell us.
Measuring HDD Power Usage
In my previous column, I discussed how to measure the power consumption of a system. In all cases, you want to measure consumption at the plug. That is how much power is being consumed in total. I pointed to one inexpensive means of doing this, which is to use the P3 Kill-A-Watt Electricity Usage Meter from P3 International.
The problem that immediately comes to mind is how to use this meter to test the power consumption of a single disk. No one is going to swap disks in and out of a desktop system to ascertain wattage. The solution is a product from the USB 2.0 Universal Drive Adapter from Newertech, which sells for $29.95 retail.
This kit consists of a small power supply to drive an HDD and a USB cable that can hook the HDD to a system. This cable supports ATA drives, including notebook and 3.5-inch drives, plus SATA drives. You plug the USB cable into your system and into the hard drive and attach the drive to its power supply. Suddenly the HDD is running. It appears to your system as a plain old USB drive. By plugging the adapter's power supply into your watt meter, you can see power consumption by this one drive. And by having the HDD hooked to your computer, you can make the drive active or let it spin undisturbed.
Apart from the power measurement considerations, this set-up is useful for peering at the contents of old HDDs without having to mount them into your system. This use is the principal use intended for this adapter.
I recently ran some parallel ATA (a.k.a IDE) drives through this set-up, and they registered around 5 watts when the disk was spinning but not doing I/O, and at around 8 watts during I/O. When compared with the 40 watts to 100 watts consumed by the processor, it's clear that despite being mechanical devices, HDD are remarkably power efficient, even in the bad old days before power consumption was on anyone's radar drive.
I pulled out an old HDD from 1995 and it consumed only 13 watts when just spinning. If you measure consumption in watts/terabyte rather than pure watts, then the progress vendors have made in the last ten years is off the charts, although this is mostly due to their abilities to increase capacity.
SATA drives run at roughly 1 watt more in quiet and I/O states, and SCSI drives run at typically 2 watts more than the ATA numbers.
To come up with at unified number for a given disk drive, the formula that is used is:
Typical power consumption = idle * .90 + write * .025 + read * .075
Since you probably won't be able to distinguish read from write in terms of power consumption (although these numbers are available from vendor specifications), you can use this formula as a basis:
Typical power consumption = idle * .90 + I/O * .10
While it's clear that hard drives should rarely be the principal focus for energy conservation on desktop systems, servers and storage boxes, their figures become more important.
Because of this, HDD vendors are stepping up their energy conservation efforts. Part of the motivation for this is the release of ENERGY STAR 4.0, which establishes low-power consumption thresholds and no vendor wants to be rejected because its components push a system over the tight baseline requirements.
In this regard, Western Digital -- one of the leading drive makers -- is moving to a new product line called GreenPower. The company claims that its 1TB SATA drive runs at 4 watts when idle and 7.5 watts during I/O (I am expecting a drive to look at and will report on this if there are variances). This would raise the bar for power efficiency on desktop drives. I expect SCSI drives will eventually be on that same power curve as well.
Save Power: Hibernate
All of this means that power consumption is rarely the correct primary factor for upgrading HDDs. Secondly, if you do upgrade your HDDs, you'll get a small lift in absolute power savings and an enormous lift in watts per GB. The best way to save power on your disks, especially on desktops, is to use the built-in power reduction technology in your operating system that puts HDDs into hibernate mode following a given portion of inactivity. Per vendor specs, this move will do the most to save energy by cutting it roughly in half for the time spent asleep.
For more information on power consumption by specific drives, visit digit-life.com.
Andrew Binstock's blog on software and technical matters can be found at http://binstock.blogspot.com.
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