This post is a follow on to the video on Systems Architecture here (video). I’ll describe how HANA, the Platform not the Database, is cutting fat from the landscape. If you have not seen the video recently it will be worth a quick look as I will only briefly recap it here.
The video, kindly sponsored by Intel, suggests that the distributed architecture we developed to collect lots of very small microprocessors into a single platform in order to solve big enterprise sized problems is evolving as multi-core microprocessors become ever more capable. In my opinion, we are starting to collapse the distributed architecture into something different.
Figure 1. A Distributed SAP Landscape
Figure 1 shows how we might deploy a series of servers to implement an SAP software landscape. Note that if we removed a couple of pieces the picture represents a platform for just about any enterprise solution. In other words, it is not just about SAP ERP solutions. I have left this in so that companies with SAP in place can see where they may be headed.
Figure 2 shows the same landscape deployed in the HANA Platform. It is a very lean deployment with all of the fat of inter-operating systems combination replaced by processes communicating over lightweight thread boundaries. Squeezing the fat out will provide significant performance benefits over the distributed deployment… it will be 2-5 times faster easily… and 2-3 times faster even if you deployed the landscape on a single server in a series of virtual machines as you have to add in the overhead of a VM plus the cost of communication over virtual networks.
Figure 2. The Landscape Collapsed into threads on the HANA Platform
The HANA Platform is very powerful stuff… and if you had the choice between SAP and a competitor, the ability to match the performance on 1/2 the hardware might provide an overwhelming advantage to HANA.Note that in this evaluation I have not included any advantages from the performance kick due to the HANA Database… so the SAP story is better still.
Those of you who heard me describe HANA while I was at SAP know that this is not a new story. It was to be the opening of the shelved book on HANA. So this post satisfies my longstanding promise to get this story documented even though the book never generated much executive enthusiasm.
The trend in systems architecture outlined in the video is being capitalized by SAP as the HANA Platform… and the advantage provided is significant. You should expect SAP customers to rapidly move to HANA to take advantage of this tight, high-performance landscape.
But the software world does not stand still for long… and there are already options emerging that approximate this approach. Stay tuned…
This is the second post (see Part 1 here) on how vendors adjust their architecture without admitting that the previous architecture was flawed. This time we’ll consider Teradata and in-memory….
When SAP HANA appeared Teradata went on the warpath with a series of posts and statements that were pointed but oddly miscued (see the references below). According to the posts in-memory was unnecessary and SAP was on a misguided journey.
Then Teradata announced Intelligent Memory and in-memory was cool. This is pretty close to an admission that SAP was right and Teradata was wrong. The numbers which drove Teradata here are compelling… 100K-200K ns to access an SSD device or 100 ns to access DRAM… a 1000X reduction… and the latency to disk is 100X worse than SSD.
Intelligent Memory was announced shortly after the release of Teradata’s columnar table type. Column-orientation is important because you need a powerful approach to compression to effectively use an expensive memory resource… and columnar provides this. But Teradata, like Greenplum, extended a row-based engine to support columns in order to get to market quick… they hoped to get 80% of the effectiveness of in-memory with only 20% of the engineering effort. The other 20% comes when you develop a new engine that fully exploits the advantages of a columnar architecture. These advanced exploits allow HANA, DB2 BLU, and Oracle 12c to execute directly on columnar data thereby avoiding decompression, fully utilizing the processor caches, and allowing sets to be operated on by super-computing vector-processing instructions. In fact, Teradata really applied the 50/20 rule… they gained 50%, maybe only 40%, of the benefits with their columnar and Intelligent Memory features… but it was easy to deploy what is in-effect an in-memory cache over their existing relational engine.
Please don’t jump to the wrong conclusion here… Intelligent Memory is a strong product. If you were to put hot data in memory, cool data in Teradata-on-SSD-or-Disk, and cold data in Hadoop and manage them as one EDW you could deploy a very cost-effective platform (see here).
Still, Teradata with Intelligent Memory is not likely to compete effectively against HANA, BLU, or 12c for raw performance… so there will be some marketing foam attached and an appeal for Teradata shops to avoid database apostasy and stick with them. You can see some of the foam in the articles below.
A quick aside here… generally a DBMS should win or lose based on price/performance. The ANSI standard makes a products features nearly, not completely but nearly, irrelevant. If you cannot win on price/performance then you blow foam. When any vendor starts talking about things like TCO you should grab your wallets… it is an appeal to foaminess to hide a weakness. I’m not calling out Teradata here… this is general warning that applies to every software vendor.
Intelligent Memory is a smart move. While it may not win in a head-to-head POC… it will be close-ish… close enough to keep the congregation in their pews. As readers know, I am not a big fan of technical religiosity… being a “Teradata-shop” is lazy… engineers we should pick the best solution and learn it. The tiered approach mentioned three paragraphs up is a good solution and non-Teradata shops should be considering it… but Teradata shops should be open to new technology as well. Still, we should pick new technology with a sensitivity to the cost of a migration… and in many cases Intelligent Memory will save business for Teradata by getting just close enough to make migration a bad trade-off. This is why it was so smart.
Back to the theme of these posts… Teradata back-tracked on the value of in-memory… and in the process admitted-without-admitting a shortcoming in their architecture. So it goes…
Next we will consider whether you should be building data warehouses on z/OS using DB2 or the DB2 Analytics Accelerator aka Netezza.
I would like to point out a very important section in the paper on Hekaton on the Microsoft Research site here. I will quote the section in total:
2. DESIGN CONSIDERATIONS
An analysis done early on in the project drove home the fact that a 10-100X throughput improvement cannot be achieved by optimizing existing SQL Server mechanisms. Throughput can be increased in three ways: improving scalability, improving CPI (cycles per instruction), and reducing the number of instructions executed per request. The analysis showed that, even under highly optimistic assumptions, improving scalability and CPI can produce only a 3-4X improvement. The detailed analysis is included as an appendix.
The only real hope is to reduce the number of instructions executed but the reduction needs to be dramatic. To go 10X faster, the engine must execute 90% fewer instructions and yet still get the work done. To go 100X faster, it must execute 99% fewer instructions. This level of improvement is not feasible by optimizing existing storage and execution mechanisms. Reaching the 10-100X goal requires a much more efficient way to store and process data.
This is important because it confirms the difference in a Level 3 and a Level 2 columnar implementation as described here. It is just not possible for a Level 2 implementation with a row-based join engine to achieve the performance of a Level 3 implementation. This will allow the Level 3 implementations: HANA, BLU, Hekaton, and Oracle 12c to distance themselves from the Level 2 products: Teradata and Greenplum; by more than 10X… and this is a very significant advantage.
This short post is intended to provide a quick warning regarding in-memory columnar and cpu requirements… with a longer post to follow.
When a row is inserted or bulk-loaded into a DBMS, if there are no indexes, the amount of cpu required is very small. The majority of the time is spent committing a transaction is the time to write a log record to persist the data.
When the same record is reformatted into a column the amount of processing required is significantly higher. The data must be parsed into columns, the values must be compressed, dictionaries may be updated, and the breadcrumbs that let the columnar data be regenerated into rows must be laid. Further, if the columnar structure are to be optimized then the data must be ordered… with a sort or some kind of index structure. I have seen academic papers that suggest that for an insert columnar processing may be 100X more than row processing… and you can see why this could be true (I apologize for not finding the reference… I’ll dig it up… as I recall I read it in a post some time back by Daniel Abadi).
Now let’s think about this… several vendors are suggesting that you can deploy their columnar features with no changes required… no new hardware… in-place. But this does not ring true if the new columnar feature requires 100X extra CPU cycles per row… or 50X… or 10X… unless you are running your database on an empty server.
This claim is a shot at SAP who, more honestly, suggests new hardware with high-end processors for their in-memory columnar product… but methinks it is marketing, not architecture, from these other folks.
IBM is presenting a DB2 Tech Talk that compares the BLU Accelerator to HANA. There are several mistakes and some odd thinking in the pitch so let me address the issues as a way to explain some things about HANA and about BLU. This blog will consider what data needs to be in-memory.
IBM like several others, continues to repeat a talking point along the lines of: “We believe that you should not have to fit all of you active data in memory…”. Let’s think about this…
Note that in the current release HANA has a constraint that all of the data in a single column, the entire vector that represents the data in that column, must be in-memory before it can be operated on. If the table is partitioned and partition-elimination is applied then the data in the partition for the column must be loaded in-memory. This is a real constraint that will be removed in a subsequent release… but it is not a very severe constraint if you think about it.
But let’s be clear… HANA does not require all data to be in-memory… it will read data from peripheral devices in and out as required just as BLU does.
Now what does this mean? Let’s walk through some scenarios.
First, let’s imagine a customer with 10TB of user data, per the scenario IBM discusses. Let’s not get into a whose product compresses better discussion and assume that both BLU and HANA will get 4X compression… so there is 2.5TB of user data to be processed.
Now let’s imagine a system with only a very little memory available for data. In other words, let’s configure both BLU and HANA so that they are full columnar databases, but not in-memory databases. In this case BLU would operate by doing constant I/O without constraint and HANA would fail whenever it could not fit a required column in memory. Note that HANA might not fail at all… it would depend on whether there was a large single un-partitioned column that was required.
This scenario is really silly though… HANA is an in-memory database, designed to keep data in-memory from the start… so SAP would not support this imaginary configuration. The fact that you could make BLU work out of memory is not really relevant as nowhere does IBM position, or reference, BLU as a disk-based column store add-on… you would just use DB2.
Now let’s configure a system to IBM’s specification with 400GB of memory. IBM does not really say how much of this memory is available to BLU for data… but for the sake of argument let’s ignore the system requirements and assume that BLU uses one-half, 200GB, as work space to process queries so that 200GB is available to store data in-memory. As you will see it does not really matter in this argument whether I am spot on here or not. So using IBM’s recommendation there is now a 200GB cache that can be used as data is paged in and out. Anyone who has ever used a data warehouse knows that caching does not work well for BI queries as each query touches large enough volumes of the data to flush the cache… so BLU will effectively be performing I/O for most queries and is back to being an out-of-memory columnar database. Note that this flushing issue is why the in-memory capabilities from Oracle and Teradata pin certain tables into memory. In this scenario HANA will operate exactly as BLU does with the constraint that any single column that in a compressed form exceeds 200GB will not be able to be processed.
Finally let’s configure a system with 5TB of memory per SAP’s recommendation for HANA. In this case BLU and HANA both fit all of the data in-memory… with 2.5TB of compressed user data in and 2.5TB of work space… and there is no I/O. This is an in-memory DBMS.
But according to the IBM Power 770 spec (here) there is no way to get 5TB of memory on a single p770 node… so to match HANA and eliminate all I/O they would require two nodes… but BLU cannot be deployed on a cluster… so on they would have to deploy on a single node and perform I/O on 20% of the data. The latency for SSD I/O is 200Kns and for disk it is 10Mns… for DRAM it is 100ns and HANA loads full cache lines so that the average latency is under 20ns… so the penalty paid by BLU is severe and it will never keep up with HANA.
There is more bunk around recommendations for the number of cores but I can make no sense of it at all so I do not know where to begin to debunk it. SAP recommends high-end Intel servers to run HANA. In the scenario above we would recommend multiple servers… soon enough there will be Haswell servers with 6TB of DRAM and this case will run on one node.
I have stated repeatedly that anytime a vendor presents a slide comparing their product to their competitors you should immediately throw them out… it will always be twisted. Don’t trust them. And don’t trust me as I work for SAP. But hopefully you can see some logic in my case. If you need an IMDB then you need memory. If you are short of memory then the IMDB operates like a columnar RDBMS with a memory cache. If you are running a BI query workload then you need to pin data in the cache or the system will thrash. Because of this SAP recommends that you get enough memory to get all of the data in… we recommend that you operate our in-memory database product in-memory…
This really the point of the post. The Five Minute Rule informs us about what data should be in-memory (see here). An in-memory database is designed from the bottom up to manage hot data in-memory. The in-memory add-ons being offered over legacy systems are very capable and should not be ignored… and as the price of memory drops the Five Minute Rule will suggest that data in-memory will account for and ever larger percentage of your EDW. But to offer an in-memory capability and recommend that you should keep the bulk of the data on disk is silly… and to state that your product has a competitive advantage because you do not recommend that all of the data managed by your in-memory feature be kept in-memory is silliness squared.
I renamed this so that Teradata folks would not get here so often… its not really about Intelligent Memory… just prompted by it. The post on Intelligent Memory is here. – Rob
Two quick comments on Teradata’s recent announcement of Intelligent Memory.
First… very very cool. More on this to come.
Next… life is going to become very hard for my readers and for bloggers in this space. The notion of an in-memory database is becoming rightfully blurred… as is the notion of column store.
Oracle blurs the concepts with words like “database in-memory” and “hybrid column compression” which is neither an in-memory database or a column store.
Teradata blurs the concept with a strong offering that uses DRAM as a block-IO device (like the old RAM-disks we used to configure on our PCs).
Teradata and Greenplum blur the idea of a column store by adding columnar tables over their row store database engines.
I’m not a fan of the double-speak… but the ability of companies to apply the 80/20 rule to stretch their architectures and glue on new advanced technologies is a good thing for consumers.
But it becomes very hard to distinguish the products now.
In future blogs I’ll try to point out differences… but we’ll have to go a little deeper into the Database Fog.
A 30 feet chunk of the cliff below the apartment building fell to Pacific Ocean. (Photo credit: Wikipedia)
Jason asked a great question in the comment section here… he asked… does Teradata’s Intelligent Memory erode HANA’s value proposition? Let me answer here in a more general way that is applicable to the general database space…
Every time a vendor puts more silicon between the CPU and the disk they will improve their performance (and increase their price). Does this erode HANA’s value proposition? Sure. Every advance by any vendor erodes every other vendor’s position.
To win business a new database product has to be faster than the competition. In my experience you have to be at least 30% faster to unseat the incumbent. If you are 50% faster you will win a lot of business. If you are 2x, 100%, faster you win nearly every time.
Therefore the questions are:
Did the Teradata announcement eliminate a set of competitors from reaching these thresholds when Teradata is the incumbent? Yup. It is very smart.
Does Intelligent Memory allow Teradata to reach these thresholds when they compete against another incumbent. Yup.
Did it eliminate HANA from reaching these thresholds when competing with Teradata? I do not think so… in fact I’m pretty sure it is not the case… HANA should still be way over the 2x threshold… but the reasons why will require a deeper dive… stay tuned.
In the picture attached a 30 foot chunk eroded… but Exadata still stands. Will it be condemned?
Note: Here is a commercial post on the SAP HANA blog site that describes at a high level why I think HANA retains a distinct architectural advantage.
If the Gartner estimates here are correct… then DRAM prices will fall 50% per year per year over the next several years… and then in 2015 non-volatile RAM (see the related articles below) will become generally available.
It has been suggested that memory prices will fall slower than data warehouses will grow (see here). That does not seem to be the case… and the combination of cheaper memory and then non-volatile memory will make in-memory databases like SAP HANA ever more compelling. In fact, as I predicted… and to their credit, Teradata is adding more memory (see here).
In the post here I listed the units of parallelism (UoP) applied by various products on a single node. Those findings are summarized in the table below.
Product
Version/HW
Cores per Node
UoP per Node
Notes
Teradata
EDW 6700H
16
32
Uses hyper-threads.
Greenplum
DCA UAP Edition
16
8
Recommends 1 Segment for each 2 cores. Maybe some multi-threading per query so it could be greater than 8 on the average… and could be 16 with hyper-threads… but not more than 32 for sure.
Exadata
X3
12
12-24
Maybe only 12… cannot find if they use hyper-threads.
A UoP is defined as the maximum number of instructions that can execute in parallel on a single node for a single query. Note that in the comments there was a lively debate where some readers wanted to count threads or processes or slices that were “active” but in a wait state. Since any program can start threads that wait I do not count these as UoP (later we might devise a new measure named units of waiting that would gauge the inefficiency in any given design by measuring the amount of waiting around required to keep the CPUs fed… maybe the measure would be valuable in measuring the inefficiency of the queue at your doctor’s office or at any government agency).
On some CPUs vendors such as Intel allow two threads to execute instructions in-parallel in a core. This is called hyper-threading and, if implemented, it allows for two UoP on a single core. Rather than constantly qualify the statements for the rest of this blog when I refer to cores I mean to imply hyper-threads.
The lively comments in the blog included some discussion of the sort of techniques used by vendors to try and keep the cores in the CPU on each node fed. It is these techniques that lead to more active I/O streams than cores and more threads than cores.
For several years now Intel and the other CPU manufacturers have been building ever more cores into their products. This has allowed them to continue the trend known as Moore’s Law. Multi-core is now a fact of life and even phones, tablets, and personal computers have multi-core chips.
But if you look at the table you can see that the database products above, even the newly announced products from Teradata and Netezza, are using CPUs with relatively few cores. The high-end Intel processors have 40 cores and the databases, with the exception of HANA, use Intel products with at most 16 cores. Further, Intel will deliver Ivy Bridge processors to the market this year with 120 cores. These vendors know this… yet they have chosen to deliver appliances with the previous generation CPUs. You might ask why?
I believe that there is an architectural reason for this (also a marketing reason covered here).
It is very hard to keep 80 cores fed with data when you have to perform block I/O. It will be nearly impossible to keep the 240 cores coming with Ivy Bridge fed. One solution is to deploy more nodes in a shared-nothing configuration with fewer cores per node… but this will be expensive requiring more power, floorspace, administration, etc. This is the solution taken by most of the vendors above. Another solution is to solve the problem without I/O with an in-memory database (IMDB) architecture. This is the solution taken by SAP with HANA.
Intel, IBM, and the rest will continue to build out using the multi-core approach for the foreseeable future. IMDB products will be able to fully utilize this product. Other products will struggle to take full advantage as we can see already… they will adapt and adjust and do what they can… but ultimately IMDB will win, I think… because there is just no other way to keep up as Moore’s Law continues to drive technology… no other way to feed the CPU engines with data fast enough.
If I am right then you will see more IMDB offerings from more vendors, including from the major vendors in the near future (note that this does not include the announcements of “database in memory” from Oracle which is not by any measure an in-memory database).
This is the underlying reason why Donald Feinberg (and Timo Elliott) are right on here. Every organization will be running in-memory… and soon.
If I were the Register I would have titled this: Raging Stuffed Elephant To Devour Two Warehouse Vendors… I love the Register… if you do not read it have a look…
This is a post is about the market implications of architecture…
Let us assume that Hadoop matures and finds a permanent place in the market. This is not certain with some folks expressing concern (here) and others boundless enthusiasm (here). So let’s assume… and consider where it might fit.
One place is in the data warehouse market… This view says Hadoop replaces the DBMS for data warehouses. But the very mature BI/DW market requires a high level of operational integrity and Hadoop is not there yet… it is advancing rapidly as an enterprise platform and I believe it will get there… but it will be 3-4 years. This is the thinking I provided here that leads me to draw the picture in Figure 1.
It is not that I believe that Hadoop will consume the data warehouse market but I believe that very large EDW’s… those over 1PB… and maybe over 500TB will be compelled by the economics of “free” to move big warehouses to Hadoop. So Hadoop will likely move down into the EDW space from the top.
Another option suggests that Big Data will be a platform unto itself. In this view Hadoop will sit beside the existing BI/DW platform and feed that platform the results of queries that derive structure from unstructured data… and/or that aggregate Big Data into consumable chunks. This is where Hadoop sits today.
In data warehouse terms this positions Hadoop as a very large independent analytic data mart. Figure 2 depicts this. Note that an analytics data mart, and a Hadoop cluster, require far less in the way of operational infrastructure… they share very similar technical requirements.
This leads me to the point of this post… if Hadoop becomes a very large analytic data mart then where will Greenplum and Netezza fit in 2-3 years? Both vendors are positioning themselves in the analytic space… Greenplum almost exclusively so. Both vendors offer integrated Hadoop products… Greenplum offers the Greenplum database and Hadoop in the same hardware cluster (see here for their latest announcement)… Netezza provides a Hadoop connector (here). But if you believe in Hadoop… as both vendors ardently do… where do their databases fit in the analytics space once Hadoop matures and fully supports SQL? In the next 3-4 years what will these RDBMSs offer in the big data analytics space that will be compelling enough to make the configuration in Figure 3 attractive?
I know that today Hadoop cannot do all that either Netezza or Greenplum can do. I understand that Netezza has two positions in the market… as an analytic appliance and as a data mart appliance… so it may survive in the mart space. But the overlap of technical requirements between Hadoop and an analytic data mart… combined with the enormous human investment in Hadoop R&D, both in the core and in the eco-system… make me wonder about where “Big Data” analytic relational databases will fit?
Note that this is not a criticism of the Greenplum RDBMS. Greenplum is a very fine product, one of the best EDW platforms around. I’ll have more to say about it when I provide my 2 Cents… But if Figure 2 describes the end state for analytics in 2-3 years then where is the place for the Figure 3 architecture? If Figure 3 is the end state then I do not see where the line will be drawn between the analytic workload that requires Greenplum and that that will run on Hadoop? I barely can see it now… and I cannot see it at all in the near future.
Both EMC Greenplum and IBM seem to strongly believe in Hadoop… they must see the overlap in functionality and feel the market momentum of Hadoop. They must see, better than most, that Hadoop wins this battle.
