Solid State Drive (SSD)

Summary

Solid State Drive (SSD)

Data Storage: Solid State Drive vs. Hard Disk Drive

Faster, solid state data storage used in place of conventional electromechanical hard disk drives (HDDs) in computers and servers.

Synopsis:

Existing hard disk drives (HDDs) use magnetically encoded disks to store and access data. While HDDs have a proven track record, newer forms of memory are making them obsolete.

"SSDs had origins in the 1950s with two similar technologies: magnetic core memory and card capacitor read-only storage. Electronic storage approaches have continued to evolve. SSDs with NAND technology, or flash memory, were first introduced by M-Micro in 1995. "They had the advantage of not requiring batteries to maintain the data in the memory (required by the prior volatile memory systems), but were not as fast as the DRAM-based solutions. Since then, SSDs have been used successfully as HDD replacements by the military and aerospace industries, as well as for other mission-critical applications" (Wikipedia, 2013).

Solid state drives (SSDs) and flash memory deliver better performance for read access and use less energy. When compared against one another, flash drives accessed data 10 to 100 times faster than HDDs, and SSDs accessed the data over 65 times faster than HDDs. They do not have this same advantage for write applications, however. In terms of energy efficiency, SSDs delivered up to 237 MB per joule, flash drives delivered up to 150 MB per joule, while HDDs topped out at 28 MB per joule. (Mordvinova, 2009)

This higher performance comes at a price: a 1 TB internal SSD from Samsung costs roughly $600, while a 1 TB internal HDD costs roughly $100. As the price of SSD and flash drives continues to drop, these newer forms of memory promise to reduce the energy consumption of computers while simultaneously improving performance.

Energy Savings: 50%

Energy Savings Rating: Limited Assessment What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

Simple Payback, New Construction (years): 63.5 What's this?

Simple Payback, Retrofit (years): 82.5 What's this?

Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:

Simple Payback = Incremental First Cost / Annual Savings

The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.

For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.

For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.

Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.

The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.

TAG Technical Score: 3.36

Details

Solid State Drive (SSD)

Data Storage: Solid State Drive vs. Hard Disk Drive

Faster, solid state data storage used in place of conventional electromechanical hard disk drives (HDDs) in computers and servers.

Item ID: 159

Sector: Commercial

Energy System: Electronics--Information Technology

Technical Advisory Group: 2013 Information Technology TAG (#8)
Average TAG Rating: 3.23 out of 5
TAG Ranking Date: 10/25/2013
TAG Rating Commentary:

Valid for performance - small energy savings. Waste of incentive money. Facebook "cold storage" is much better concept - just turn OFF hard drives when not needed.
Difficult to implement and verify.
I believe this has to be a leading emerging tech.
Not an ET.
Cost per gig still high but coming down.
Long term storage may require a duplicate storage strategy.
Very hard to control what tenants buy, long payback.
SSDs not only provide much faster data read and write operations, but also have a much smaller energy footprint due to their low voltage operation.

Synopsis:

Existing hard disk drives (HDDs) use magnetically encoded disks to store and access data. While HDDs have a proven track record, newer forms of memory are making them obsolete.

Baseline Example:

Baseline Description: Reading and Writing data to an electromechanical 1 TB SATA disk
Baseline Energy Use: 175 kWh per year per unit

Comments:

The baseline technology uses spinning disks, like CD's. Spinning the disk uses power. The power used by a spinning disk, 24/7/365 is about 175 kWh/yr. For purposes of apples-to-apples comparison, assume that this is a one terabyte drive. Assume that it is idle about half of the time and varies between streaming audio or video, database calculations, and maximum read-write loading when active. (Otto, 2013)

Manufacturer's Energy Savings Claims:

"Typical" Savings: 20%
Savings Range: From 1% to 60%

Comments:

We have not been able to find specific levels of energy savings claims from manufacturers. However, they will readily say that they do save energy, and they give product specifications from which one can calculate savings with certain assumptions about use, such as how much each drive is in idle, sleep, or hibernate mode. Complicating the calculation, however, is determining an apples-to-apples comparison. As of the end of 2013, enterprise-quality SSDs are mostly available in 512 GB capacity and less, whereas HDDs are easily available up to 4 TB capacities. If an apples-to-apples comparison is a 512 GB SSD vs. the same capacity HDD, then it is easy to show 80% savings or more (Otto, 2013). However, if an apples-to apples comparison is what you may be likely to buy -- that is, for instance, a 2 TB HDD or four 512 GB drives, you may not save anything at all. We believe that most manufacturers would be comfortable in claiming that SSDs will save about 20% or more of the energy of HDDs.

Best Estimate of Energy Savings:

"Typical" Savings: 50%
Low and High Energy Savings: 10% to 93%
Energy Savings Reliability: 3 - Limited Assessment

Comments:

This estimate is based on a standard hard drive using 175 kWh per year, and a solid state drive using 20 kWh. This is a fairly typical estimate for a 1 terabyte drive in Nov. 2013. That gives about 89% savings. With this technology improving so rapidly, and the standard hard disk not as fast, we are assuming slight continued improvement by the time this is published, so we rounded the savings up to 90%. That will depend, however, on several assumptions. One variable will be how much each drive is in idle, sleep, or hibernate mode. Complicating the calculation is determining an apples-to-apples comparison. As of the end of 2013, enterprise-quality SSDs are mostly available in 512 GB capacity and less, whereas HDDs are easily available up to 4 TB capacities. If an apples-to-apples comparison is a 512 GB SSD vs. the same capacity HDD, then it is easy to show 80% savings or more (Otto, 2013). However, if an apples-to apples comparison is what you may be likely to buy -- that is, for instance, a 2 TB HDD or four 512 GB drives, you may not save anything at all. The estimate of 50% savings is based on the idle-active ratio assumed by Otto, and assuming your choice is to buy a single 2 TB HDD in place of four 512 GB or two 1 TB SSDs. Typical examples of these might save 30% over HDDs. Furthermore, since using less energy in storage access would reduce the cooling load in the data center, and would save some cooling energy as well. We estimate the average data center Power Usage Effectiveness is 2.6, so it is fair to multiply the storage energy savings by 1.67 to get energy savings equivalent to 50% of the storage energy used by the equivalent HDD.

This estimate of savings does not take into account reduced cooling needs. SSDs can withstand much higher temperatures than HDDs and virtually require "no" cooling. If this could be implemented throughout a data center to significantly reduce cooling loads, the total savings from implementing this technology could be much greater, depending on other measures already taken to save energy.

Energy Use of Emerging Technology:

87.5 kWh per unit per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Technical Potential:
Units: unit
Currently no data available.

First Cost:

Installed first cost per: unit
Emerging Technology Unit Cost (Equipment Only): $600.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $50.00
Baseline Technology Unit Cost (Equipment Only): $100.00

Comments:

This estimate was based on a spot comparison in November 2013 on Newegg.com, comparing the cost of a client-quality SSDs: SAMSUNG 840 EVO MZ-7TE1T0BW 2.5" 1TB SATA III TLC Internal Solid State Drive (SSD) or Crucial M500 960GB SATA 2.5" 7mm (with 9.5mm adapter) Internal Solid State Drive CT960M500SSD1 versus various 1TB client-quality HDDs available at under $100. The installation charge is based on an estimate from the WSU Energy Program IS staff estimate of 30 to 50 minutes to install, assuming it can be done with internal staff.

Cost Effectiveness:

Simple payback, new construction (years): 63.5

Simple payback, retrofit (years): 82.5

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Detailed Description:

From Wikipedia (Wikipedia, 2013): “A solid-state drive (SSD) (also known as a solid-state disk or electronic disk, though it contains no actual "disk" of any kind, nor motors to "drive" the disks) is a data storage device using integrated circuit assemblies as memory to store data persistently...SSDs had origins in the 1950s with two similar technologies: magnetic core memory and card capacitor read-only store (CCROS)."

Electronic storage approaches have continued to evolve. SSDs with NAND technology, or flash memory, were first introduced by M-Micro in 1995. "They had the advantage of not requiring batteries to maintain the data in the memory (required by the prior volatile memory systems), but were not as fast as the DRAM-based solutions. Since then, SSDs have been used successfully as HDD replacements by the military and aerospace industries, as well as for other mission-critical applications" (Wikipedia, 2013).

Still, until 2009, most SSDs used dynamic random access memory (DRAM). It is orders of magnitude faster than HDDs, but is more expensive, and it is "volatile" memory, meaning the data needs to be refreshed periodically (several times a second) or it is lost. Since 2009, most SSDs have used NAND or "flash" memory. This is a non-volatile memory, so it uses no power to retain the data when it is just being stored. This makes it significantly more energy-efficient than either DRAM or HDDs.

The primary advantage of SSDs over HDDs is a read speed orders of magnitude (approaching 100 times) faster than HDDs. Write speeds on a new SSD can also be very fast. However, once an SSD has fully been used, write performance degrades noticeably, proceeding more at the erase speed (since data is having to be erased to make room for more data), which is much slower, and may not be faster than an HDD. Thus, they are very well suited to low write/high read applications. ( Energy Star, 2013)

Solid state drives are well-established in the market and are easily available from several manufacturers, notably Seagate, Toshiba, Western Digital Technologies, and Samsung. A few examples are listed in the Product Information section.

Product Information:
Crucial M500, Internal Solid State Drive CT960M500SSD1 Samsung, 840 EVO MZ-7TE1T0BW 2.5" 1TB SATA III TLC Internal Solid State Drive (SSD) Intel, SSD DC S3500 Series SSDSC2BB600G401 2.5" 600GB SATA III MLC Internal Solid State Drive (SSD) Toshiba, 512GB Q Series Pro Internal Solid State Drive Western Digital Technologies, WD SiliconDrive A100 Seagate, Eneterprise SATA SSD, 480 GB, mod. no. ST480FN0021

Standard Practice:

The standard technology that solid state drives (SSDs) replace in computers, consumer electronic devices, and servers are electromechanical hard disk drives (HDDs) with Serial Advanced Technology Attachment (SATA) bus interface.

Development Status:

SSDs are easily available, and have been for several years. Prices have dropped dramatically in 2012 and 2013, and are expected to continue to do so. They are now affordable enough that many enterprises are beginning to deploy them for performance reasons more than for energy savings. "the percentage of IT administrators using SSDs on disk arrays and servers was up to 20% in 2012."

Non-Energy Benefits:

The main advantage of SSDs over HDDs is speed. The following table compares various speed-related characteristics of SDDs to HDDs.

Characteristic	Solid State Drive	Hard Disk Drive
Start-up time	Almost instantaneous. May need a few milliseconds to come out of an automatic power-saving mode.	Several seconds
Random access time	Typically under 0.1 ms	2.9 to 12 ms
Read latency (delay) time	Low	Much higher than SSDs. Latency will depend on the location of the data on the disk relative to the read-head.
Data transfer rate	Consumer products typically 100 to 600 MB/s. Enterprise-quality devices can have data transfer rates of 2 GB/s or higher.	Typically 140 MB/s
Fragmentation	Since location on the disk does not affect transfer rate, fragmentation of files is not a problem.	File fragmentation can affect access time because each fragment may require spinning of the disk to access. Defragmentation is required periodically for maintenance.

Because of the almost instantaneous access time, these are ideal in applications where many users are trying to access the same drive at the same time.

SSDs also operate almost totally silently and can tolerate much higher temperatures and typically do not require special cooling. HDDs lose life expectancy over 95 F (35 C), and reliability is compromised above 131 F (55 C). SSDs also tend to be more reliable in general, though failures are sometimes more catastrophic that hard drives. They are also much more resistance to shock and vibration, making them a good choice for places where this is an issue, such as laptops.

End User Drawbacks:

Solid state drives, as of late 2013, are still significantly more expensive than standard hard disks, and wear out more quickly.

According to Adrian Otto, on his blog:

Reasons why NOT to switch to SSD drives

If you need a lot of storage. The cost per GB of the SSD storage is considerably higher than the cost per GB of SATA storage, even considering the performance and power savings.
If you are constantly writing to the hard drives over and over. SSD drives to have a limited duty cycle, and in general may be less durable than regular hard drives. Eventually they do wear out, just for different reasons than drives with moving parts. However, most of the drives that are on the market today are rated for MTBF durability that’s comparable to what traditional hard drives offer.
You run your data center on solar power (yeah, sure you do). Seriously, if your cost for power is dirt cheap, and you need a lot of storage, then regular hard drives may be a better value for you. (Otto, 2013)

The other thing to be aware of is that with lots of re-writing, performance will degrade. At advertised and new speeds, SSDs are dramatically faster than HDDs, but performance degrades noticeably with use. Partly that is because erase speed is much slower than write speed, and once a disk is full, any writing will be over-writing old data, slowing performance from new down by a factor of five or more. In addition, software may not be written to fully take advantage of SSD performance, so the improvements over HDDs may not be as much as advertised (Polte, 2009). Some researchers question whether an SSD, once full, under current practices, really performs that much better than HDDs. (Boboila, 2011)

Operations and Maintenance Costs:

Baseline Cost: $0.00 per: unit per year
Emerging Technology Cost: $0.00 per: unit per year

Comments:

Other than replacement costs, there is really no maintenance to SSDs or HDDs. HDDs do need to be defragmented once in a while, but that can be set up to happen automatically during slow computational times through software, so the labor and out-of-pocket costs will be minimal. On average, SSDs do not last as long as HDDs, so replacement costs will be higher, but either one should last as long as most IT hardware is kept these days (4-5 years).

Effective Life:

Anticipated Lifespan of Emerging Technology: 5 years

Comments:

A few years ago, some of the concerns about SSDs is that they were less reliable than HDDs and there was a possibility of catastrophic failure, losing all the data from an entire SSD. Those concerns are still relevant, but much less so than a few years ago. An SSD does have a limited number of read-write cycles before they fail, but this has been improving, and most drives now come with management software that controls which sectors are used for wear-leveling, so that most sectors will get even wear, which helps extend the life of the drive. Enterprise-quality drives can now considered to be essentially error-free and have a 15-20 year or more technical life. In practice, most of this kind of equipment is upgraded in five years or less, since the quality, performance, and storage density will likely be much greater in 5 years, justifying an upgrade long before failure.

Competing Technologies:

The main competing technology is solid state hybrid drives (SSHDs). They have a mechanical hard drive at the core and NAND (flash) memory to supplement. They come with controllers to use the flash memory for the frequently-used data for fast access, and use the hard drive for less frequently accessed data, taking advantage of the best properties of both technologies. They provide much faster access to frequently-used data than a hard drive, and much more economical storage for longer-term storage, providing the best of both worlds.

Reference and Citations:

Adrian Otto, 01/08/2013. Does SSD Power Savings Pay for Itself?
Adrian Otto's Blog
Special Notes: The short answer is "no." A solid state drive (he didn't specify the size -- 1 Terabyte?), using Adrian Otto's assumptions, saves, on average, about 80% of the energy of a standard hard drive, saving about 20 W over a hard drive, or 175 kWh per year per drive for a server running 24/7, or nearly $16/yr. With an expected lifetime of five years, they would save about $80 each. Add HVAC savings, and you could get $100 savings per drive. As of mid-2013, they cost $2-300 more than a standard hard drive.

Milo Polte, 06/20/2009. Understanding Performance in Solid State Disks
Los Alamos National Laboratory

S. Y. Panitkin, 06/05/2009. Study of Solid State Drives performance in PROOF distributed analysis system
Brookhaven National Laboratory

Junghee Lee, 02/24/2011. A Semi-Preemptive Garbage Collector for Solid State Drives
Oak Ridge National Laboratory

ORNL, 10/27/2011. Coordinated Garbage Collection for RAID Array of Solid State Disks
Oak Ridge National Laboratory

Energy Star, 09/17/2013. Better Management of Data Storage
Energy Star

Leslie Johnston, 10/05/2012. A Storage Technology Cage Match
Library of Congress

JEDEC, 01/01/2013. Solid State Drives
Joint Electron Devices Engineering Council
Special Notes: In September 2010 JEDEC announced the publication of two widely anticipated standards for solid state drives: JESD218 Solid-State Drive (SSD) Requirements and Endurance Test Method and JESD219 Solid-State Drive Endurance Workloads.

Simona Boboila, 04/06/2011. Performance Models of Flash-based Solid-State Drives for Real Workloads
Northeastern University

Feng Chen, 04/05/2011. Hystor: Making the Best Use of Solid State Drives in High Performance Storage Systems
Intel Labs/Ohio State University

Peter Desnoyers, 05/11/2012. Analytic Modeling of SSD Write Performance
Northeastern University

Olga Mordvinova, 10/14/2009. USB Flash Drives as an Energy Efficient Storage Alternative
University of Heidelberg
Special Notes: Power Point presentation of the paper submitted for the 2009 10th IEEE/ACM International Conference on Grid Computing, Banff, Alberta, Canada

Olga Mordvinova, 10/13/09. USB Flash Drives as an Energy Efficient Storage
University of Heidelberg
Special Notes: Paper presented at the 2009 10th IEEE/ACM International Conference on Grid Computing, Banff, Alberta, Canada. Shows that flash drives can be a viable alternative to hard drives when used appropriately, and can save energy.

Wikipedia, 11/12/2013. Solid-state drive
Wikipedia

Rank & Scores

Solid State Drive (SSD)

2013 Information Technology TAG (#8)

Technical Advisory Group: 2013 Information Technology TAG (#8)
TAG Ranking: 10 out of 57
Average TAG Rating: 3.23 out of 5
TAG Ranking Date: 10/25/2013
TAG Rating Commentary:

Valid for performance - small energy savings. Waste of incentive money. Facebook "cold storage" is much better concept - just turn OFF hard drives when not needed.
Difficult to implement and verify.
I believe this has to be a leading emerging tech.
Not an ET.
Cost per gig still high but coming down.
Long term storage may require a duplicate storage strategy.
Very hard to control what tenants buy, long payback.
SSDs not only provide much faster data read and write operations, but also have a much smaller energy footprint due to their low voltage operation.

Technical Score Details

TAG Technical Score: 3.4 out of 5

How significant and reliable are the energy savings?
Energy Savings Score: 3.0 Comments:

While I expect the savings to be significant I have not seen any data to that effect.
Savings are significant, reliability is unclear.
Hard drive electrical consumption is generally becoming more energy efficient. Flash drive storage is still expensive.
Lower energy use means more savings.
This a tough one. In the right application the savings are great. For most applications the savings non-existent.
Improved performance will probably drive this measure; limited short-stroke HDD applications.
No real savings compared to the same amount of HDD, The short-stroked HDD appears to have more energy savings benefits than SSD.
Only special cases yield savings
Contrary to some of the information delivered in the webinar, SSD has significant energy savings potential for all storage tiers.
"Good, but only relevant for certain applications:Utilize SSD for high I/O applications•Tier 0 – between memory (RAM) and storage (drives)"

How great are the non-energy advantages for adopting this technology?
Non-Energy Benefits Score: 4.2
Comments:

This seems like something that will happen anyway as the costs of the technology drops. Is this really an energy play or are the IT benefits so great that it will happen for other reasons?
Faster transfer speeds and lower latencies.
In the right application, these displace a lot of gear. They also really push up processing speeds and equipment accessibility.
Improved performance will probably drive this measure
The increased response time is benefit to the end-user but the bandwidth into the drive may be the same so it may not provide a noticeable benefit to the end user.
Speed of read-write operations is very high.
Very significant increase in I/O performance, which can have ancillary benefits including better server utilization rates.
"No moving parts•Faster Response (low access latency)•Low power•High cost / GB•Little impact to shock, vibration•Lifetime based on write-endurance"

How ready are product and provider to scale up for widespread use in the Pacific Northwest?
Technology Readiness Score: 3.6
Comments:

As costs come down this will become more attractive. Public good programs can help accelerate this.
Difficult to assess.
Since most SSDs are the same 2.5" form factor as their hard drive counterparts, they can usually be installed in pre-existing systems.
Given that the applicable market is so limited, it looks to me like the vendors are well ready for any uptake.
Equipment are commercially available and already installed in some equipment.
There are both on-board products as well as storage array equipment from a half-dozen or so vendors. A few leading storage vendors (i.e. NetApp) are beginning to enter the market also.

How easy is it to change to the proposed technology?
Ease of Adoption Score: 2.9
Comments:

Alternative back up will be needed. Long term storage capability has not been proven.
But, expensive...
Even though their prices are coming down, they're still expensive.
This is not a plug and play technology. It's got to be carefully applied in just the right circumstances.
Not sure how well it will work in a server environment. Assume it will work as well as it does in desktop/laptop system.
Although this is not a good retrofit opportunity, IT managers can easily specify SSD use in new purchases.
"fairly easy switch, but again, it only applies to certain applicationsUtilize SSD for high I/O applications•Tier 0 – between memory (RAM) and storage (drives)"

Considering all costs and all benefits, how good a purchase is this technology for the owner?
Value Score: 3.1
Comments:

Value will increase as costs come down.
The best solution for very high speed access, but not for most basic storage needs.
Value comes form non energy benefits
This is an expensive way to save energy. It's a great way to push up speeds, the value of which is hard to quantify.
Performance is great but cost is a barrier and savings are limited to special cases.
I believe this is quite expensive, though not quite sure

Completed:
12/4/2013 3:58:20 PM
Last Edited:
12/4/2013 3:58:20 PM