A couple of specifications for SSD endurance are in common use today: Terabytes Written (TBW) and Drive Writes Per Day (DWPD). Both are different ways to express the same thing. It seems that one vendor will specify endurance using TBW, while another will specify DWPD. How do you compare the two?
First, some definitions. “Terabytes Written” is the total amount of data that can be written into an SSD before it is likely to fail. “Drive Writes Per Day” tells how many times you can overwrite the entire capacity of the SSD every single day of its usable life without failure during the warranty period. Since both of these are guaranteed specifications, then your drive is most likely to last a lot longer than the number given by the SSD’s maker.
To convert between the two you must know the disk’s capacity and the warranty period. If drive maker gives you TBW but you want to know DWPD you would approach it Continue reading
Yesterday SanDisk announced a new low-end family of SSDs that the company said would sell: “at a price point on par with HDDs. (Pricing comparison dependent upon capacity.)” The sub-headline states: “Z400s SSD Brings New Levels of Affordability to Replace Hard Drives…”
The release provided no actual prices to back up this claim.
So how does this work? Can you actually now buy a 1TB SSD for cheaper than a 1TB HDD? Not at all. Instead you have to look at things a little differently using a concept that I frequently explained five years ago when SSDs were pretty new – that very low capacity SSDs can be cheaper than HDDs.
This post’s graph plots this out. It’s a chart of HDD and SSD prices over a range of capacities. It’s on a log-log scale, but it works well on a standard linear chart as well. Note that prices are for 2010, and prices have come down significantly for both SSDs and HDDs since then. This means that the numbers on the X and Y axes need adjustment to bring them to today’s levels, but the shape of the curves would remain the same.
The red line represents SSD costs over the range of capacities, and the black line represents HDDs. Although HDDs are cheaper than SSDs Continue reading
From time to time IT managers ask The SSD Guy if there’s an easy way to compare SSDs made with MLC flash against those made using eMLC flash. Most folks understand that eMLC flash is a less costly alternative to SLC flash, both of which provide longer wear than standard MLC flash, but not everyone realizes that eMLC’s superior endurance comes at the cost of slower write speed. By writing to the flash more gently the technology can be made to last considerably longer.
So how do you compare the two? OCZ introduced MLC and eMLC versions of the same SSD this week, and this provides a beautiful opportunity to explore the difference.
As you would expect, the read parameters are all identical. This stands to reason, since Continue reading
So why would this appear in the pages of The SSD Guy blog?
In a nutshell, coffee demand is falling thanks to increased use of SSDs. It’s not that people were giving their computers coffee to speed them up, nor were managers ladling coffee into their employees to get more out of them when the real problem was slow PC performance. Instead it’s about boot-up time.
For the past few decades the average worker comes into the office, turns on the PC, then goes to the coffee room to get the morning’s first cup of brew while the PC slowly finds its way to full operation. While in the coffee room that worker may encounter workmates, and delve into a heady conversation about last night’s TV programs, or a sporting event, or even politics. This might turn that one-cup coffee-room visit into a 2-cup session.
Now that savvy bosses are Continue reading
Someone recently asked The SSD Guy if there is a way to determine whether an SSD is SLC, MLC, eMLC or TLC.
I found it a little odd to be asked this, since most vendors tell what kind of flash they use in an SSD’s specifications, especially if it’s SLC.
Not finding it there then the next thing I would look at is the price. Raw SLC NAND flash now sells for about 6-10 times as much as its MLC counterpart, so an SSD with a price of around $1/GB is likely to be MLC and one that sells for around $10/GB is probably SLC.
TLC SSDs are really rare. There is the Continue reading
Samsung recently introduced its 3D V-NAND-based 850 SSD which, according to The Tech Report, uses the same MEX controller as the company’s 3-bit planar SSD, the 840, introduced last year.
Samsung said in its keynote speech at the 2013 Flash Memory Summit that V-NAND consumes an average of 27% less power and runs at least 20% faster than its planar counterpart in an SSD application, all while providing ten times the endurance. It’s only natural to assume that this would allow designers to produce a V-NAND SSD that would significantly outperform its planar NAND counterpart.
In a move that The SSD Guy wishes he had thought of for himself, SanDisk has begun to help corporations upgrade their fleets of notebook PCs by replacing their HDDs with SSDs.
SanDisk calls this program STAR for: “SanDisk Tech-Assisted Refresh”. According to the press release: “Through the STAR program, SanDisk relieves IT departments of having to manage all aspects of upgrading corporate laptops such as, endpoint inventory analysis, employee service scheduling, system upgrades, data migration, daily progress reporting, post-upgrade analysis and support.”
SanDisk points out that PCs slow down with disk utilization and software updates, lowering users’ productivity. Often faster storage can solve that problem.
This is not an altogether new Continue reading
Erik Logan of Pogo Linux sent me a link to an amusing & informative video he and his company put together called A Brief History of SSDs. In the video Erik (pictured) tells of Pogo Linux’ experience with SSDs.
The company has a lot of hands-on SSD experience: Pogo Linux ships servers and storage and has ramped SSD shipments (as a percent of all drives) from single digits three years ago to the point where SSDs now account for 31% of all drives they ship. Erik shared with me that: “Sorting through the Continue reading
Earlier this month Western Digital’s HGST division invited The SSD Guy to a launch of a number of products. On the HDD side there were:
- 6TB air HDD, HGST’s last air-filled enterprise HDD
- 8TB helium HDD, an incremental upgrade of last year’s 6TB helium HDD
- 10TB shingled helium HDD (pictured)
I view these as very solid evidence that HDD costs will continue to stay an order of magnitude cheaper than SSD costs, thwarting the price-per-gigabyte crossover that others have been predicting for years.
In fact, since my last post on the price crossover in 2011, very little has changed.
It’s safe to assume that the HDD industry will Continue reading