Category: SQLFire

Thinking About the Pivotal Announcements…

Yesterday I provided a model for how business sees open source as a means to be profitable (here). This is the game Pivotal seems to be playing with their release of Hadoop, Gemfire, HAWQ, and Greenplum into open source. I do not know their real numbers… so they may need more or fewer additional customers than the mythical company to get back to break-even. But it is unlikely that any company can turn the corner from a license-based revenue stream to a recurring revenue stream in a year… so Pivotal must be looking at a loss. And when losses come it is usual to cut costs… to cut R&D.

There has already been a brain-drain out of the database ranks at Pivotal as they went “all in” on Hadoop. They likely hope for an open source community to pick up the slack… but there is not a body of success I can see in building a community to engineer a commercial product-turned-open. This is especially problematic for Gemfire, an old technology that has been in the commercial space for a very long time. HAWQ has to compete for database resources with the other Hadoop RDBMS technologies… that will be difficult. Greenplum has a chance as it is based on PostgreSQL… but it is a long way away from the current PostgreSQL code base these days. There is danger here.

The bottom line… Greenplum and HAWQ and Gemfire have become risky propositions for both the current customer base and for new customers. I’ll leave it to you to evaluate the risk as this story unfolds. Still, with the risk comes reward… the cost of acquiring Greenplum will drop dramatically and today Greenplum is a competitive product. In addition, if Greenplum gains some traction, it will put price pressure on the other database products. Note that HAWQ was already marked down to open source price levels… and part of Pivotal’s problem was that HAWQ was eating at the Greenplum market. With these products priced at similar levels there becomes some weirdness in choosing… but the advantage is to customers looking at Greenplum.

One great outcome comes for Pivotal Hadoop customers… the fact that Hortonworks will more-or-less subsume Pivotal Hadoop leaves those folks in a better place than before.

If you consider the thought experiment you would have to ask yourself why a company that was breaking even would take this risky route? It could be that they took the route because they were not breaking even and this was a possible path to get even. Also consider… open sourcing code is the modern graceful way to retire an unprofitable product line.

This is sound thinking by Pivotal… during the creation, EMC gave Pivotal several unprofitable troubled assets and these announcements give Pivotal a path forward. If the database product line cannot carry their weight then they will go into maintenance mode and slowly fade. Too bad… as you know I consider Greenplum a solid product whose potential was wasted. But Pivotal has a very nice product in Cloud Foundry… and they clearly see this as their route to profitability and to an IPO… a route that no longer includes a significant contribution from database products.

Open Source is Not a Market…

This post is more about the technology business than about technology… but it may be relevant as you try to sort out winners and losers… and this sort of sorting is important if you consider new companies who may, or may not, succeed in the long run.

To make my point let us do a little thought experiment. Imagine a company doing $100M in revenue with a commercial, not open source, database product. They win the $100M in revenue by competing with Oracle, IBM, Microsoft, Teradata, et cetera… and maybe competing a little here and there with some open source products.

Let’s assume that they make 50% of their revenue from services and support, and that their average sale is $2M… so they close 25 deals a year competing in this market. Finally, let’s assume that they break-even each year and spend 20% of their revenues on R&D. The industry average for support services is 20%.. so with each $2M sale they add $400K in recurring revenue.

They are considering making their product open source. Let’s assume that they make the base product free… and provide some value-added offering that costs $200K for the average buyer. Further, they offer a support package for the same $400K/year customers currently pay. How does the math work out?

Let’s baseline against the 25 deals/year…

If they make 25 sales and every buyer buys both the support package and the value-added offer the average sale drops from $2M to $200K, sales revenue drops from $50M to $5M, the annual revenue drops from $100M to $55M… and the company loses $45M. So… starting off they need to make 225 more sales just to break even. But now it gets complicated… if they sell 5 extra deals then in the next year they earn $2M extra in support fees… so if they sell 113 extra deals in year one then in year two they have made up the entire $45M difference and they are back to break-even going forward. If it takes them 2 years to get the extra recurring revenue then they lose money in year two… but are back to break-even in year three.

From here it gets even more complicated. The mythical company above sells the baseline of 25 new copies a year with an enterprise sales force that is expensive. There is no way that the same sales force that services 25 sales/year could service 100+ extra deals. So either costs go up or the 100+ extra customers becomes unattainable. We might hope that the cost of sales will drop way off as the sales price moves to $200K. This is not unreasonable… but certainly not guaranteed. Further, if you are one of the existing sales-staff then you have to sell 10X just to make the same commission. Finally these numbers assume that every customer buys the value-add and gets enterprise-level support. Reality will be something less than this.

We might ask: is it even possible to sell 100+ more with the same product in the same market? Let us be clear that the market the database product plays in has not changed. Open Source is not a market. All we have done is reduced the sales price for the product with some hope that price is a significant driver in the market.

This is not meant as an academic exercise. Tomorrow we will consider how this thought experiment applies to Pivotal’s announcements last week… and to the future of Pivotal’s database assets (here).

Data Recovery in HANA, TimesTen, and SQLFire

There is a persistent myth, like a persistent cough, that claims that in-memory databases lose data when a hardware failure takes down a node because memory is volatile and non-persistent. This myth is marketing, not architecture.

Most RDBMS products: including Oracle, TimesTen, and HANA; have three layers where data exists: in-memory (think SGA for Oracle), in the log, and on disk. The normal process goes like this:

  1. A write transaction arrives
  2. The transaction is written to the log file and committed… this is a very quick process with 1 sequential I/O… quicker still if the log file is on a SSD device
  3. The query updates the in-memory layer; and
  4. After some time passes, saves the in-memory data to disk.

Recovery for these databases is easy to understand:

  • If a hardware failure occurs and #1 but before #2 the transaction has not been committed and is lost.
  • If a hardware failure occurs after #2 but before #3 the transaction is committed and the database is rebuilt when the node restarts from the log file.
  • If a hardware failure occurs after #3 but before #4 the same process occurs… the database is rebuilt when the node restarts from the log file.
  • If a hardware failure occurs after #4 the database is rebuilt from the disk copy.

SQLFire uses a different approach (from here):

“Unlike traditional distributed databases, SQLFire does not use write-ahead logging for transaction recovery in case the commit fails during replication or redundant updates to one or more members. The most likely failure scenario is one where the member is unhealthy and gets forced out of the distributed system, guaranteeing the consistency of the data. When the failed member comes back online, it automatically recovers the replicated/redundant data set and establishes coherency with the other members. If all copies of some data go down before the commit is issued, then this condition is detected using the group membership system, and the transaction is rolled back automatically on all members.”

Redundant in-memory data optimizes transaction throughput but requires twice the memory. There are options to persist data to disk… but these options provide an approach that is significantly slower than the write-ahead logging used by TimesTen and HANA (and Oracle and Postgres, and …).

The bottom line: IMDBs are designed in the same manner as other, disk-based, DBMSs. They guarantee that comitted data is safe… everytime.

P.S.

See here for how these DBMSs compare when a BI/analytic workload is applied.

SQLFire, Exalytics, TimesTen, and HANA… a quick comparison

Gemfire

As you may have noticed I’m looking at in-memory databases (IMDB) these days… Here are some quick architectural observations on VMWare‘s SQLFire, Oracle’s Exalytics and TimesTen offerings, and SAP HANA.

It is worth noting up front that I am looking to see how these products might be used to build a generalized data mart or a data warehouse… In other words I am not looking to compare them for special case applications. This is important because each of these products has some extremely cool features that allow them to be applied to application-specific purposes with a narrow scope of data and queries… maybe in a later blog I can try to look at some narrow use-cases.

Further, to make this quick blog tractable I am going to assume that the mart/dw problem to be solved requires more data than can fit on one server node… and I am going to ignore features that let queries access data that resides on disk… in-memory or bust.

Finally I will assume that the SQL dialect supported is sufficient and not drill into details there. I will look at architecture not SQL features…

Simply put I am going to look at a three characteristics:

  • Will the architecture support ad hoc queries?
  • Does the architecture support scale-out?
  • Can we say anything with regards to price/performance expectations?

Exalytics is a smart-aggregate store that sits over an Oracle database to offload aggregate query workload (see my previous post here or the Rittman Mead post here which declares: “Oracle Exalytics uses a specially enhanced version of Oracle TimesTen, Oracle’s in-memory database, to cache commonly used aggregates used in dashboards, analyses and other BI objects.” Exalytics does not support a scale-out shared-nothing architecture but it can scale up by adding nodes with new aggregate data. Queries access data within the aggregate structure and it is not possible to join to data off the Exalytics node… so ad hoc is out. Within these limits, which preclude Exalytics from being considered as a general platform for a mart or warehouse, Exalytics provides dictionary-based compression which should provide around 5X compression to reduce the amount of memory required and reduce the amount of hardware required.

TimesTen can do more. It is a general RDBMS. But it was designed for OLTP. I assume that the reason that Oracle has not rolled it out as a general-purpose data mart or data warehouse has to do with constraints that grow from those OLTP architectural roots. For example, BI queries run longer and require more data than a OLTP query… and even with data in-memory temporary storage is required for each query… and memory utilization is a product of the amount of data required and the amount of time the data has to inhabit memory… so BI queries put far more pressure on an in-memory DBMS. There are techniques to mitigate this… but you have to build the techniques in from the ground up.

I imagine that this is why TimesTen works for Exalytics, though. A OLAP query against a pre-aggregated cube does not graze an entire mart or warehouse. It is contained and “small data” (for my wacky take re: Exalytics and Exadata see here).

TimeTen is not sharded… so scalability is an issue. Oracle gets around this nicely by allowing you to partition data across instances and have the application route queries to the appropriate server. But this approach will not support joins across partitions so it severely limits scalability in a general-purpose mart or warehouse.

SQLFire is a very interesting new product built on top of Gemfire… and therefore mature from the start. SQLFire is more scalable than TimesTen/Exalytics. It supports sharded data in a cluster of servers. But SQLFire has the limitation that it cannot join data across shards (they call them partitions… see here) so it will be hard to support ad hoc queries… They provide the ability to replicate tables to support any sort of joins. If, for example, you replicate small dimension tables to coexist with sharded fact tables all joins are supported. This solution is problematic if you have multiple fact tables which must be joined… and replication of data uses more memory… but SQLFire has the foundation in place to become BI-capable over time.

Performance in an in-memory database comes first and foremost from eliminating disk I/O. All three IMDB product provide this capability. Then performance comes from the efficient use of compression. TimeTen incorporates Oracles dictionary-based “columnar” compression (I so hate this term… it is designed to make people think that Oracle products are sort-of columnar… but so far they are not). Then performance comes from columnar projection… the ability to avoid touching all data in a row to process a query. Neither TimesTen nor SQLFire are columnar databases. Then performance comes from parallel execution. Neither TimesTen nor SQLFire can involve all cores on a single query to my knowledge.

Price comes from compression as well. The more highly compressed the data is the less memory required to store it. Further, if data can be used without decompressing it, then less working memory is required. As noted, TimesTen has a compression capability. SQLFire does not appear to compress data. Neither can use compressed data. Note that 2X compression cuts the amout of memory/hardware required in half or more… 4X cuts it to a quarter… and so on. So this is significant.

Now for some transparency… I started the research for this blog, and composed a 1st draft, last Spring while I was at EMC Greenplum. I am now at SAP working with HANA. So… I will not go into HANA at great length… but I will point out that: HANA fully supports a shared-nothing architetcture… so it is fully scalable; HANA is fully parallel and able to use all cores for each query; HANA fully supports columnar tables so it provides deep compression and the ability to use the compressed data in execution. This is not remarkable as HANA was designed from the bottom up to support both BI and OLTP workloads while TimesTen and SQLFire started from a purely OLTP architectural foundation.

References:

vFabric SQLFire User’s Guide

Oracle Times Ten In-Memory Database Architectural Overview

Real-time Analytics and BI: Part 1 – Singing for my Dinner

Several months ago I was invited to a dinner attached to a data science summit… with the price being that I had to deliver a 5 minute talk… I had to sing for my dinner. The result was this thinking on real-time analytics and the Toyota Prius.

Real-time analytics implies two things:
 
  1. Changes in the data are evaluated continuously; and
  2. The results of the analysis are used or displayed continuously.
In a Toyota Prius we can see two examples of real-time analytics.
 
The first is in the anti-lock braking system. There data reflecting the pressure on the brake pedal and on rotation of each wheel is sent to a computer that analyzes the results and adjusts the brake pressure on each wheel so that all four wheels turn at the same rate and the car stops in a straight line.
 
Note that the analytics are real-time and the results are used immediately without human intervention. This is important. It makes little sense to spend the money to capture and analyze data in real-time if the results are not actionable in near-real-time.
 
Think for a moment about the BI systems built over the last 20 years. First we captured and analyzed monthly data… and acted on that data within a 30-day window. Then we increased the granularity of the data to weekly and slightly adjusted the reports to reflect the finer granularity… and acted on the data within 7 days. Then we adjusted the data to daily and acted on the results each day. Then we adjusted the data to hourly and reacted even more quickly. These changes often did not fundamentally change the business processes driven by the data… they just made the processes more sensitive to the fine-grained information.
 
But if the data-driven business process takes ten minutes to complete… for example it takes ten minutes for staff to pick inventory, package the results, and load a delivery truck; could there be a return on the investment expense of developing a continuous, real-time analytic? I think not. There may, however, be ROI associated with a new robotic pick, package, and load process…
 
There is another possibility… If sometimes the pick, package, and load takes ten minutes and sometimes it takes fifteen minutes then the best solution is to perform the analytics on the current state on-demand… when there are resources to support the process. This maximizes the use of the resources without changing the business process.
 
The point here is that real-time requires a re-think… or at least a deep-think. The business process may have to change significantly to support real-time analytics.
 
The second real-time system in the Prius illustrates the problem. On the dashboard the Prius displays, in real-time, the state of the hybrid gas-electric system. It shows whether the battery is charging or discharging… it shows whether the car is being driven using the electric or the internal-combustion engine. It is one of the most beautiful dashboard displays you have ever seen… and executives everywhere must look at it and wonder why they cannot get such a beautiful display of the state of their business… after-all…  BI dashboards are “the thing”.
 
But the Prius display is useless. There is no action you would take while driving based on this real-time display.From a decision-making view it represents useless and expensive flash (that helps to sell the Prius…).
 
So… approach real-time analytics with a deep-think. Look for opportunities like the anti-lock braking system where real-time analytics can be embedded into automatic business processes. Avoid flashy dashboards that do not present actionable data.
 
In-memory databases (IMDB) such as SAP HANA, Oracle TimesTen, and VMWare SQLFire promise to enable real-time analytics… and this promise is real… the opportunities can and will revolutionize the enterprise over time…  but a revolution is not the same old BI at a finer granularity… it is much more significant than that. Heads will roll.

Cloud Computing and Data Warehousing: Part 4 – IMDB Data Warehouse in a Cloud

In the previous blogs on this topic (Part 1, Part 2, Part 3) I suggested that:

  1. Shared-nothing is required for an EDW,
  2. An EDW is not usually under-utilized,
  3. There are difficulties in re-distributing sharded, shared-nothing data to provide elasticity, and
  4. A SAN cannot provide the same IO bandwidth per server as JBOD… nor hit the same price/performance targets.

Note that these issues are tied together. We might be able to spread the EDW workload over so many shards and so many SANs that the amount of I/O bandwidth per GB of EDW data is equal to or greater than that provided on a DW Appliance. This introduces other problems as there are typically overhead issues with a great many nodes. But it could work.

But what if we changed the architecture so that I/O was not the bottleneck? What if we built a cloud-based shared-nothing in-memory database (IMDB)? Now the data could live on SAN as it would only be read at start-up and written at shut-down… so the issues with the disk subsystem disappear… and issues around sharing the SAN disappear. Further, elasticity becomes feasible. With an IMDB we can add and delete nodes and re-distribute data without disk I/O… in fact it is likely that a column store IMDB could move column-compressed data without re-building rows. IMDB changes the game by removing the expense associated with disk I/O.

There is evidence emerging  that IMDB technology is going to change the playing field (see here).

Right now there are only a few IMDB products ready in the market:

  • TimeTen: which is not shared-nothing scalable, nor columnar, but could be the platform for a very small, 400GB or less (see here), cloud-based EDW;
  • SQLFire: which is semi-shared-nothing scalable (no joins across shards), not columnar, but could be the platform for a larger, maybe 5TB, specialized EDW;
  • ParAccel: which is shared-nothing scalable, columnar, but not fully an IMDB… but could be (see C. Monash here); or
  • SAP HANA: which is shared-nothing, IMDB, columnar and scalable to 100TB (see here).

So it is early… but soon enough we should see real EDWs in the cloud and likely on Amazon EC2, based on in-memory database technologies.

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