EMC World keynote stage, storage, vblocks, and cloud...
EMC announced today a couple of new twists on the flash/SSD storage end of the product spectrum. Specifically,
They now support all flash/no-disk storage systems. Apparently they have been getting requests to eliminate disk storage altogether. Probably government IT but maybe some high-end enterprise customers with low-power, high performance requirements.
They are going to roll out enterprise MLC flash. It’s unclear when it will be released but it’s coming soon, different price curve, different longevity (maybe), but brings down the cost of flash by ~2X.
EMC is going to start selling server side Flash. Using storage FAST like caching algorithms to knit the storage to the server side Flash. Unclear what server Flash they will be using but it sounds a lot like a Fusion-IO type of product. How well the server cache and the storage cache talks is another matter. Chuck Hollis said EMC decided to redraw the boundary between storage and server and now there is a dotted line that spans the SAN/NAS boundary and carves out a piece of the server which is sort of on server caching.
Interesting to say the least. How well it’s tied to the rest of the FAST suite is critical. What happens when one or the other loses power, as Flash is non-volatile no data would be lost but the currency of the data for shared storage may be another question. Also having multiple servers in the environment may require cache coherence across the servers and storage participating in this data network!?
Some teaser announcements from Joe’s keynote:
VPLEX asynchronous, active active supporting two datacenter access to the same data over 1700Km away Pittsburgh to Dallas.
New Isilon record scalability and capacity the NL appliance. Can now support a 15PB file system, with trillions of files in it. One gene sequencer says a typical assay generates 500M objects/files…
Embracing Hadoop open source products so that EMC will support Hadoop distro in an appliance or software only solution
Pat G also showed EMC Greenplum appliance searching a 8B row database to find out how many products have been shipped to a specific zip code…
Had a talk the other week with an storage executive about SSD and NAND cost trends. It seemed that everyone thought that $/GB for SSD was going to overtake (be less costly) than enterprise class disk sometime in 2013. But it appeared that NAND costs weren’t coming down as fast as anticipated and now this was going to take longer than expected.
A couple of other things are going on in the enterprise disk market that are also having an effect on the relative advantage of SSDs over disks. Probably, most concerning to SSD market is enterprise storage’s new penchant for sub-LUN tiering.
Automated sub-LUN storage tiering
The major storage vendors all currently support some form of automated storage tiering for SSD storage (NetApp’s Flash Cache does this differently but the impact on NAND storage requirements is arguably similar). Presumably, such tiering should take better advantage of any amount of SSD/NAND storage available to a storage system.
Prior to automated sub-LUN storage tiering, one had to move a whole LUN to SSDs to take advantage of its speed. However, I/O requests or access are not necessarily at the same intensity for all blocks of a LUN. So one would typically end up with an SSD LUN with a relatively few blocks being heavily accessed while the vast majority of its blocks would not be being hit that much. We paid the high price of SSD LUNs gladly to get the high performance for those few blocks that really needed it.
However, with sub-LUN tiering or NAND caching, one no longer has to move all the blocks of a LUN into NAND storage to gain its benefits. One can now just have the system identify those select blocks which need high performance and move those blocks and those blocks only to NAND storage. The net impact of sub-LUN tiering or NAND caching is that one should require less overall NAND storage to obtain the same performance as one had previously with SSDs alone.
On the other hand, some would say that making the performance advantages of NAND be available at a lower overall cost might actually increase the overall amount of NAND shipments. Also with automated sub-LUN tiering in place, this removes all the complexity needed previously to identify which LUNs needed higher performance. Reducing such complexity should increase SSD or NAND market penetration.
Nonetheless, I feel that given todays price differential of SSDs over enterprise disk, the people buying SSDs today have a very defined need for speed and would have paid the price anyways for SSD storage. Anything we do to make satisfying that need with less SSD or NAND storage should reduce the amount of SSDs shipped today.
But getting back to that price crossover point, as the relative price of NAND on $/GB comes down, having an easy way to take advantage of its better performance should increase its market adoption, even faster than price would do alone.
A head assembly on a Seagate disk drive by Robert Scoble (cc) (from flickr)
Yesterday, it was announced that Hitachi General Storage Technologies (HGST) is being sold to Western Digital for $4.3B and after that there was much discussion in the tweeterverse about the end of enterprise disk as we know it. Also, last week I was at a dinner at an analyst meeting with Hitachi, where the conversation turned to when disks will no longer be available. This discussion was between Mr. Takashi Oeda of Hitachi RSD, Mr. John Webster of Evaluator group and myself.
Why SSDs will replace disks
John was of the opinion that disks would stop being economically viable in about 5 years time and will no longer be shipping in volume, mainly due to energy costs. Oeda-san said that Hitachi had predicted that NAND pricing on a $/GB basis would cross over (become less expensive than) 15Krpm disk pricing sometime around 2013. Later he said that NAND pricing had not come down as fast as projected and that it was going to take longer than anticipated. Note that Oeda-san mentioned density price cross over for only 15Krpm disk not 7200rpm disk. In all honesty, he said SATA disk would take longer, but he did not predict when
I think both arguments are flawed:
Energy costs for disk drives drop on a Watts/GB basis every time disk density increases. So the energy it takes to run a 600GB drive today will likely be able to run a 1.2TB drive tomorrow. I don’t think energy costs are going to be the main factor to drives disks out of the enterprise.
Density costs for NAND storage are certainly declining but cost/GB is not the only factor in technology adoption. Disk storage has cost more than tape capacity since the ’50s, yet they continue to coexist in the enterprise. I contend that disks will remain viable for at least the next 15-20 years over SSDs, primarily because disks have unique functional advantages which are vital to enterprise storage.
Most analysts would say I am wrong, but I disagree. I believe disks will continue to play an important role in the storage hierarchy of future enterprise data centers.
NAND/SSD flaws from an enterprise storage perspective
All costs aside, NAND based SSDs have serious disadvantages when it comes to:
Data retention – the problem with NAND data cells is that they can only be written so many times before they fail. And as NAND cells become smaller, this rate seems to be going the wrong way, i.e, today’s NAND technology can support 100K writes before failure but tomorrow’s NAND technology may only support 15K writes before failure. This is not a beneficial trend if one is going to depend on NAND technology for the storage of tomorrow.
Sequential access – although NAND SSDs perform much better than disk when it comes to random reads and less so, random writes, the performance advantage of sequential access is not that dramatic. NAND sequential access can be sped up by deploying multiple parallel channels but it starts looking like internal forms of wide striping across multiple disk drives.
Unbalanced performance – with NAND technology, reads operate quicker than writes. Sometimes 10X faster. Such unbalanced performance can make dealing with this technology more difficult and less advantageous than disk drives of today with much more balanced performance.
None of these problems will halt SSD use in the enterprise. They can all be dealt with through more complexity in the SSD or in the storage controller managing the SSDs, e.g., wear leveling to try to prolong data retention, multi-data channels for sequential access, etc. But all this additional complexity increases SSD cost, and time to market.
SSD vendors would respond with yes it’s more complex, but such complexity is a one time charge, mostly a one time delay, and once done, incremental costs are minimal. And when you come down to it, today’s disk drives are not that simple either with defect skipping, fault handling, etc.
So why won’t disk drives go away soon. I think other major concern in NAND/SSD ascendancy is the fact that the bulk NAND market is moving away from SLC (single level cell or bit/cell) NAND to MLC (multi-level cell) NAND due to it’s cost advantage. When SLC NAND is no longer the main technology being manufactured, it’s price will not drop as fast and it’s availability will become more limited.
Some vendors also counter this trend by incorporating MLC technology into enterprise SSDs. However, all the problems discussed earlier become an order of magnitude more severe with MLC NAND. For example, rather than 100K write operations to failure with SLC NAND today, it’s more like 10K write operations to failure on current MLC NAND. The fact that you get 2 to 3 times more storage per cell with MLC doesn’t help that much when one gets 10X less writes per cell. And the next generation of MLC is 10X worse, maybe getting on the order of 1000 writes/cell prior to failure. Similar issues occur for write performance, MLC writes are much slower than SLC writes.
So yes, raw NAND may become cheaper than 15Krpm Disks on a $/GB basis someday but the complexity to deal with such technology is also going up at an alarming rate.
Why disks will persist
Now something similar can be said for disk density, what with the transition to thermally assisted recording heads/media and the rise of bit-patterned media. All of which are making disk drives more complex with each generation that comes out. So what allows disks to persist long after $/GB is cheaper for NAND than disk:
Current infrastructure supports disk technology well in enterprise storage. Disks have been around so long, that storage controllers and server applications have all been designed around them. This legacy provides an advantage that will be difficult and time consuming to overcome. All this will delay NAND/SSD adoption in the enterprise for some time, at least until this infrastructural bias towards disk is neutralized.
Disk technology is not standing still. It’s essentially a race to see who will win the next generations storage. There is enough of an eco-system around disk that will keep pushing media, heads and mechanisms ever forward into higher densities, better throughput, and more economical storage.
However, any infrastructural advantage can be overcome in time. What will make this go away even quicker is the existance of a significant advantage over current disk technology in one or more dimensions. Cheaper and faster storage can make this a reality.
Moreover, as for the ecosystem discussion, arguably the NAND ecosystem is even larger than disk. I don’t have the figures but if one includes SSD drive producers as well as NAND semiconductor manufacturers the amount of capital investment in R&D is at least the size of disk technology if not orders of magnitude larger.
Disks will go extinct someday
So will disks become extinct, yes someday undoubtedly, but when is harder to nail down. Earlier in my career there was talk of super-paramagnetic effect that would limit how much data could be stored on a disk. Advances in heads and media moved that limit out of the way. However, there will come a time where it becomes impossible (or more likely too expensive) to increase magnetic recording density.
I was at a meeting a few years back where a magnetic head researcher predicted that such an end point to disk density increase would come in 25 years time for disk and 30 years for tape. When this occurs disk density increase will stand still and then it’s a certainty that some other technology will take over. Because as we all know data storage requirements will never stop increasing.
I think the other major unknown is other, non-NAND semiconductor storage technologies still under research. They have the potential for unlimited data retention, balanced performance and sequential performance orders of magnitude faster than disk and can become a much more functional equivalent of disk storage. Such technologies are not commercially available today in sufficient densities and cost to even threaten NAND let alone disk devices.
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So when do disks go extinct. I would say in 15 to 20 years time we may see the last disks in enterprise storage. That would give disks an almost an 80 year dominance over storage technology.
But in any event I don’t see disks going away anytime soon in enterprise storage.
InPhase Technologies Drive & Media (c) 2010 InPhase Technologies, All Rights Reserved (From their website)
Although InPhase Technologies and a few other startups had taken a shot at holographic storage over time, there has not been any recent innovation here that I can see.
Ecosystems matter
The real problem (which InPhase was trying to address) is to build up an ecosystem around their technology. In magnetic disk storage, you have media companies, head companies, and interface companies; in optical disk (Blu-Ray, DVDs, CDs) you have drive vendors, media vendors, and laser electronic providers; in magnetic tape, you have drive vendors, tape head vendors, and tape media vendors, etc. All of these corporate ecosystems are driving their respective technologies with joint and separate R&D funding, as fast as they can and gaining economies of scale from specialization.
Any holographic storage or any new storage technology for that matter would have to enter into the data storage market with a competitive product but the real trick is maintaining that competitiveness over time. That’s where an ecosystem and all their specialized R&D funding can help.
Market equavalence is fine, but technology trend parity is key
So let’s say holographic storage enters the market with a 260GB disk platter to compete against something like Blu-ray. Well today Blu-ray technology supports 26GB of data storage in single layer media, costing about $5 each and a drive costs about ~$60-$190. So to match todays Blu-ray capabilities holographic media would need to cost ~$50 and the holographic drive about ~$600-$1900. But that’s just today, dual layer Blu-Ray is available coming on line soon and in the labs, a 16-layer Blu-ray recording was demonstrated in 2008. To keep up with Blu-ray, holographic storage would need to demonstrate in their lab more than 4TB of data on a platter and be able to maintain similar cost multipliers for their media and drives. Hard to do with limited R&D funding.
As such, I believe it’s not enough to achieve parity to other technologies currently available, any new storage technology really has to be at least (in my estimation) 10x better in costs and performance right at the start in order to gain some sort of foothold that can be sustained. To do this against Blu-ray, optical holographic would need to start at 260GB platter for $5 with a drive at $60-$190 – just not there yet.
But NAND Flash/SSDs did it!
Yes, but the secret with NAND/SSDs was that they emerged from e-prom’s a small but lucrative market and later their technology was used in consumer products as a lower cost alternative/lower power/more rugged solution to extremely small form factor disk devices that were just starting to come online. We don’t hear about extremely small factor disk drives anymore because NAND flash won out. Once NAND flash held the market there, consumer product volumes were able to drive costs down and entice the creation of a valuable multi-company/multi-continent ecosystem. From there, it was only a matter of time before NAND technologies became dense and cheap enough to be used in SSDs addressing the more interesting and potential more lucrative enterprise data storage domain.
So how can optical holographic storage do it?
Maybe the real problem for holographic storage was its aim at the enterprise data storage market, perhaps if they could have gone after some specialized or consumer market and carved out a niche, they could have created an ecosystem. Media and Entertainment has some pretty serious data storage requirements which might be a good match. InPhase was making some inroads there but couldn’t seem to put it altogether.
So what’s left for holographic technology to go after – perhaps medical imaging. It would play to holographic’s storage strengths (ability to densely record multiple photographs). It’s very niche-like with a few medical instrument players developing MRI, cat scans and other imaging technology that all require lot’s of data storage and long-term retention is a definite plus. Perhaps, if holographic technology could collaborate with a medical instrument consortium to establish a beachhead and develop some sort of multi-company ecosystem, it could move out from there. Of course, magnetic disk and tape are also going after this market, so this isn’t a certainty but there may be others markets like this out there, e.g., check imaging, satellite imagery, etc. Something specialized like this could be just the place to hunker down, build an ecosystem and in 5-7 years, emerge to attack general data storage again.
(c) 2011 Silverton Consulting, Inc., All Rights Reserved
We return to our periodic discussion of storage system performance, this time on SPECsfs(r)2008 benchmark results for NFS file serving ops per second vs. system reported memory size. For some obscure reason, I was very intrigued with this chart.
Chart description
We have broken the data out to show those system that only used DRAM in system memory with only hard disk drives and those systems that also included either NAND cache in system memory or SSDs. Current SPECsfs2008 results show 33 systems with DRAM and disk drives and only 6 using SSDs or NAND cache for NFS results.
The horizontal axis shows system memory size for the systems under test and doesn’t include SSD capacity (considered drive capacity by SPECsfs2008) size but does include NAND cache size (considered system memory by SPECsfs2008). The vertical axis shows maximum NFS throughput operations per second attained by the storage. The two lines are Excel generated linear regressions across the two sets of data (DRAM-Disk only systems and SSD or NAND caching systems).
Discussion of results
Given the limited data we probably can’t conclude much from the SSD-NAND linear regression line other than it’s different and somewhat less than what can be gained on average from a system using DRAM and disk only. Also the regression coefficient (R**2) of either linear regression is not that great (~0.62 for DRAM-Disk only and ~0.69 for SSD or NAND use) which might be stretching any real discussion based on statistical normalcy. Nevertheless, one question that emerges is why would SSD or NAND use not generate an relatively equivalent amount of NFS throughput as systems with DRAM only?
Obviously, NAND-SSDs access times are not as fast as DRAM. Thus, if I had 800GB of DRAM, I could potentially access data faster than if I had 800GB of NAND cache or SSDs, all things being equal. However, when talking about access time frames at the sub-msec level one would think it wouldn’t make that much of a difference, but apparently it does.
Also, given the limited data on SSDs vs. NAND cache use, it’s hard to make any distinction between these two types of systems but one can hope that as more data comes in, we can answer this as well. Another question is whether SSD capacity should be considered system memory or drive capacity for benchmark purposes. SPECsfs2008 states that SSD size should be considered drive capacity but that’s open to some debate which more data could help resolve.
Finally, missing from SPECsfs2008 reports is any statement of system cost. As such, it’s impossible to add any measure of relative cost effectiveness factor to this discussion. However, given the current price differential (on $/GB) between DRAM and NAND memory or SSD capacity, one could probably conclude that on a cost effectiveness basis the relative advantages of DRAM only systems might diminish. But without system cost information that’s difficult to quantify.
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Aurora's Perception or I Schrive When I See Technology by Wonderlane (cc) (from Flickr)
Some of these technologies were in development prior to 2000, some were available in other domains but not in storage, and some were in a few subsystems but had yet to become popular as they are today. In no particular order here are my top 10 storage technologies for the decade:
NAND based SSDs– DRAM and other technology solid state drives (SSDs) were available last century but over the last decade NAND Flash based devices have dominated SSD technology and have altered the storage industry forever more. Today, it’s nigh impossible to find enterprise class storage that doesn’t support NAND SSDs.
GMR head– Giant Magneto Resistance disk heads have become common place over the last decade and have allowed disk drive manufacturers to double data density every 18-24 months. Now GMR heads are starting to transition over to tape storage and will enable that technology to increase data density dramatically
Data Deduplication – Deduplication technologies emerged over the last decade as a complement to higher density disk drives as a means to more efficiently backup data. Deduplication technology can be found in many different forms today, ranging from file and block storage systems, backup storage systems, to backup software only solutions.
Thin provisioning – No one would argue that thin provisioning emerged last century but it took the last decade to really find its place in the storage pantheon. One almost cannot find a data center class storage device that does not support thin provisioning today.
Scale-out storage – Last century if you wanted to get higher IOPS from a storage subsystem you could add cache or disk drives but at some point you hit a subsystem performance wall. With scale-out storage, one can now add more processing elements to a storage system cluster without having to replace the controller to obtain more IO processing power. The link reference talks about the use of commodity hardware to provide added performance but scale-out storage can also be done with non-commodity hardware (see Hitachi’s VSP vs. VMAX).
Storage virtualization – server virtualization has taken off as the dominant data center paradigm over the last decade but a counterpart to this in storage has also become more viable as well. Storage virtualization was originally used to migrate data from old subsystems to new storage but today can be used to manage and migrate data over PBs of physical storage dynamically optimizing data placement for cost and/or performance.
LTO tape – When IBM dominated IT in the mid to late last century, the tape format dejour always matched IBM’s tape technology. As the decade dawned, IBM was no longer the dominant player and tape technology was starting to diverge into a babble of differing formats. As a result, IBM, Quantum, and HP put their technology together and created a standard tape format, called LTO, which has become the new dominant tape format for the data center.
Cloud storage – Unclear just when over the last decade cloud storage emerged but it seemed to be a supplement to cloud computing that also appeared this past decade. Storage service providers had existed earlier but due to bandwidth limitations and storage costs didn’t survive the dotcom bubble. But over this past decade both bandwidth and storage costs have come down considerably and cloud storage has now become a viable technological solution to many data center issues.
iSCSI – SCSI has taken on many forms over the last couple of decades but iSCSI has the altered the dominant block storage paradigm from a single, pure FC based SAN to a plurality of technologies. Nowadays, SMB shops can have block storage without the cost and complexity of FC SANs over the LAN networking technology they already use.
FCoE – One could argue that this technology is still maturing today but once again SCSI has taken opened up another way to access storage. FCoE has the potential to offer all the robustness and performance of FC SANs over data center Ethernet hardware simplifying and unifying data center networking onto one technology.
No doubt others would differ on their top 10 storage technologies over the last decade but I strived to find technologies that significantly changed data storage that existed in 2000 vs. today. These 10 seemed to me to fit the bill better than most.
(c) 2010 Silverton Consulting, Inc., All Rights Reserved
It’s been a while since we reported on Storage Performance Council (SPC) Least Response Time (LRT) results (see Chart of the month: SPC LRT[TM]). This is one of the charts we produce for our monthly dispatch on storage performance (quarterly report on SPC results).
Since our last blog post on this subject there have been 6 new entries in LRT Top 10 (#3-6 &, 9-10). As can be seen here which combines SPC-1 and 1/E results, response times vary considerably. 7 of these top 10 LRT results come from subsystems which either have all SSDs (#1-4, 7 & 9) or have a large NAND cache (#5). The newest members on this chart were the NetApp 3270A and the Xiotech Emprise 5000-300GB disk drives which were published recently.
The NetApp FAS3270A, a mid-range subsystem with 1TB of NAND cache (512MB in each controller) seemed to do pretty well here with all SSD systems doing better than it and a pair of all SSD systems doing worse than it. Coming in under 1msec LRT is no small feat. We are certain the NAND cache helped NetApp achieve their superior responsiveness.
What the Xiotech Emprise 5000-300GB storage subsystem is doing here is another question. They have always done well on an IOPs/drive basis (see SPC-1&-1/E results IOPs/Drive – chart of the month) but being top ten in LRT had not been their forte, previously. How one coaxes a 1.47 msec LRT out of a 20 drive system that costs only ~$41K, 12X lower than the median price(~$509K) of the other subsystems here is a mystery. Of course, they were using RAID 1 but so were half of the subsystems on this chart.
It’s nice that some turnover in this top 10 LRT. I still contend that response time is an important performance metric for many storage workloads (see my IO throughput vs. response time and why it matters post) and improvement over time validates my thesis. Also I received many comments discussing the merits of database latencies for ESRP v3 (Exchange 2010) results, (see my Microsoft Exchange Perfomance ESRP v3.0 results – chart of the month post). You can judge the results of that lengthy discussion for yourselves.
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As always, we welcome any constructive suggestions on how to improve our storage performance analysis.
We have been discussing NAND technology for quite awhile now but this month I ran across an article in IEEE Spectrum titled “a SPIN to REMEMBER – Spintronic memories to revolutionize data storage“. The article discussed a form of magneto-resistive random access memory or MRAM that uses quantum mechanical spin effects or spintronics to record data. We have talked about MRAM technology before and progress has been made since then.
Many in the industry will recall that current GMR (Giant Magneto-resistance) heads and TMR (Tunnel magneto-resistance) next generation disk read heads already make use of spintronics to detect magnetized bit values in disk media. GMR heads detect bit values on media by changing its electrical resistance.
Spintronics however can also be used to record data as well as read it. These capabilities are being exploited in MRAM technology which uses a ferro-magnetic material to record data in magnetic spin alignment – spin UP, means 0; spin down, means 1 (or vice versa).
The technologists claim that when MRAM reaches its full potential it could conceivably replace DRAM, SRAM, NAND, and hard disk drives or all current electrical and magnetic data storage. Some of MRAM’s advantages include unlimited write passes, fast reads and writes and data non-volatilility.
MRAM reminds me of old fashioned magnetic core memory (in photo above) which used magnetic polarity to record non-volatile data bits. Core was a memory mainstay in the early years of computing before the advent of semi-conductor devices like DRAM.
Back to future – MRAM
However, the problems with MRAM today are that it is low-density, takes lots of power and is very expensive. But technologists are working on all these problems with the view that the future of data storage will be MRAM. In fact, researchers at the North Carolina State University (NCSU) Electrical Engineering department have been having some success with reducing power requirements and increasing density.
As for data density NCSU researchers now believe they can record data in cells approximating 20 nm across, better than current bit patterned media which is the next generation disk recording media. However reading data out of such a small cell will prove to be difficult and may require a separate read head on top of each cell. The fact that all of this is created with normal silicon fabrication methods make doing so at least feasible but the added chip costs may be hard to justify.
Regarding high power, their most recent design records data by electronically controlling the magnetism of a cell. They are using dilute magnetic semiconductor material doped with gallium maganese which can hold spin value alignment (see the article for more information). They are also using a semiconductor p-n junction on top of the MRAM cell. Apparently at the p-n junction they can control the magnetization of the MRAM cells by applying -5 volts or removing this. Today the magnetization is temporary but they are also working on solutions for this as well.
NCSU researchers would be the first to admit that none of this is ready for prime time and they have yet to demonstrate in the lab a MRAM memory device with 20nm cells, but the feeling is it’s all just a matter of time and lot’s of research.
Fortunately, NCSU has lots of help. It seems Freescale, Honeywell, IBM, Toshiba and Micron are also looking into MRAM technology and its applications.
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Let’s see, using electron spin alignment in a magnetic medium to record data bits, needs a read head to read out the spin values – couldn’t something like this be used in some sort of next generation disk drive that uses the ferromagnetic material as a recording medium. Hey, aren’t disks already using a ferromagnetic material for recording media? Could MRAM be fabricated/layed down as a form of magnetic disk media?? Maybe there’s life in disks yet….
