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
A recent conversation with some fellow analysts revealed a puzzling set of claims. EMC, at its EMC World conference (May 3-7) claimed to be the leader in flash array shipments. The very next week, in the same Las Vegas hotel, IBM also claimed leadership in flash.
Who do you believe?
- EMC is counting XtremIO Arrays as units shipped and according to Gartner Group held the #1 market share position with a 31.1% share, which is over a ten percentage point share lead
- IBM is counting capacity of PBs shipped with all of their flash storage solutions: The FlashSystem 840, 900, V840, V9000, DS8000, plus the XIV systems, Storwize V7000, IBM Flash DAS, and IBM PCIe Adapters
- NetApp is the leader if you count total flash systems shipped (NetApp-branded plus privately-branded systems) spanning multiple years as their SANtricity operating system and E-Series platforms have sold over 750,000 units
- Pure Storage uses its 700% growth to show that it’s the #1 fastest-growing flash storage company
- Then, if you want to compare any vendor’s total all flash array (AFA) systems sold this past year against hybrid storage arrays, Nimble Storage beats any of the AFA vendors.
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
This replacement for the company’s Z-Drive 4000 series is a complete redesign with an obsession for performance. OCZ tells me that they moved from a 2-hop design to a 1-hop by using the PMC Princeton PCIe SSD controller, and have passed the University of New Hampshire Interoperability Labs’ compliance tests to NVMe 1.1B compliance.
But how does it perform? Well the 1-hop design helps reduce latency (which is just starting to overshadow IOPS in users’ minds) and the latency of this SSD is significantly lower than competing NVMe SSDs: between 25-30μs, figures that OCZ tells me are very consistent, a big plus for enterprise applications. As for IOPS, the device can perform under a 70/30 Read/Write load at 330K.
The 6000 series is provided in both standard MLC and eMLC for those who want the security of eMLC and are willing to sacrifice a little performance to sleep better at night.
This product is a good fit for the market needs, and shows how devoted OCZ and its parent Toshiba are to providing high performance in the SSD marketplace.
I have to admit that it’s embarrassing when The SSD Guy misses something important in the world of flash storage, but I only recently learned of a paper that Baidu, China’s leading search engine, presented at the ASPLOS conference a year ago. The paper details how Baidu changed the way they use flash to gain significant benefits over their original SSD-based systems.
After having deployed 300,000 standard SSDs over the preceding seven years, Baidu engineers looked for ways to achieve higher performance and more efficient use of the flash they were buying. Their approach was to strip the SSD of all functions that could be better performed by the host server, and to reconfigure the application software and operating system to make the best of flash’s idiosyncrasies.
You can only do this if you have control of both the system hardware and software.
The result was SDF, or “Software-Defined Flash”, a card that 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
With a webcast in the style of the big system makers like EMC and Oracle, SanDisk announced its InfiniFlash flash appliance. InfiniFlash is a box that crams a whopping 500 terabytes into only 3U of rack space.
How big is 500 terabytes? It’s more bytes than SanDisk’s entire flash output for 2001.
SanDisk boasts that InfiniFlash is a “category-defining product”, and pointed to the fact that IDC, who provided support for the roll-out, created a new “Big Data Flash” storage product category for this device.
The system boasts performance of one million random-read IOPS, which is impressive, but doesn’t give much indication of how it performs in standard enterprise dataflow, which is generally assumed to consist of a 70/30 split of reads and writes. (I should mention here that Objective Analysis published a survey of users’ IOPS and latency needs which can be purchased on our website.)
Price is a major focus for this product. SanDisk says that it will sell systems bundled with software at less than Continue reading
IBM has unveiled its new IBM FlashSystem V9000, an all-new offering that supports scale-up and scale-out flash growth models. The FlashSystem V9000 is an upgrade to the company’s FlashSystem V840 product. IBM also introduced the new IBM FlashSystem 900, the follow-on generation to the IBM FlashSystem 840. A full complement of software services (including snapshots and replication) is bundled with the product.
Over 4,000 IBM FlashSystems have shipped since the brand was introduced two years ago causing the company’s bit shipments to outpace the combined shipments of the second and third-ranked flash array providers.
The IBM FlashSystem V9000 comes in a 6U package that incorporates twelve IBM MicroLatency modules that provide 57TB of RAID 5 usable capacity, which then blooms to 285TB with IBM Real-time Compression. The proprietary modules provide more consistent performance than SSD-based systems – the system is as fast when it is 90% full as it is when only 10% of its total capacity is in use.
IBM tells us that the FlashSystem V9000 is not simply a virtualized node built up from a number of IBM FlashSystem 900 systems, but is a single, integrated system purpose-built to address the needs and focus of cloud, analytics, mobile/social and security. It supports seamless concurrent capacity increases up to its 2.2 petabyte upper limit when real-time compression is used.
IBM’s FlashSystem V9000 is currently available and carries a 7-year warranty as well as an optional 5-year “TCO” lease that IBM has priced to be cheaper than the high-performance disk arrays it has been designed to replace. This is intended to bring peace of mind to skittish would-be flash users.
An acquaintance pointed out that EMC has published a case study detailing how one of its divisions, EMC Corporate IT, decided to use an EMC Isilon storage system over other competing candidates:
After considering various storage solutions, EMC IT selected EMC Isilon® scale-out storage as the foundation for a new Hadoop-as-a-Service (HDaaS) offering.
My acquaintance wondered exactly which systems EMC IT evaluated before selecting an EMC array, and whether or not there was even the option of choosing a product from any of the numerous competing storage array vendors. He pointed out how embarrassing it would have been if this case study had been written by a competitor to tout its win at EMC IT.
You really have to wonder why EMC published this case study. Its customers take it for granted that the company will use its own offerings, and would probably leave in droves if it did not.
To paraphrase an old saying: “No EMC employee ever got fired for choosing EMC!”