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• Free tools for SQL Server - Automating Execution Plan Analysis

  - by jchang

  Since this topic is being discussed, I will plug my own tools, SQL Exec Stats and (a little dated) documentation the main capability is cross-referencing index usuage with specific execution plans. another feature is generating execution plans for all stored procedures in a database, along with the index usage cross-reference. There are several sources of execution plans or plan handles, this could be a live trace, a previously saved trace, previously saved sqlplan files, from dm_exec_cached_plans,...(read more)

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• TPC-H Benchmarks on SQL Server 2014 with Columnstore

  - by jchang

  Three TPC-H benchmark results were published in April of this year at SQL Server 2014 launch, where the new updateable columnstore feature was used. SQL Server 2012 had non-updateable columnstore that required the base table to exist in rowstore form. This was not used in the one published TPC-H benchmark result on SQL Server 2012, which includes two refresh stored procedures, one inserting rows, the second deleting rows. It is possible that the TPC-H rules do not allow a view to union two tables?...(read more)

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• Supermicro motherboards and systems

  - by jchang

  I used to buy SuperMicro exclusively for my own lab. SuperMicro always had a deep lineup of motherboards with almost every conceivable variation. In particular, they had the maximum memory and IO configuration that is desired for database servers. But from around 2006, I became too lazy to source the additional components necessary to complete the system, and switched to Dell PowerEdge Tower servers. Now, I may reconsider as neither Dell or HP are offering the right combination of PCI-E slots. Nor...(read more)

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• SSDs at PASS 2012

  - by jchang

  There were 7 companies exhibiting SSD products as PASS this year, and one with a product to support SSD storage. This is not counting Dell, EMC and HP who have SSD products, but were at PASS for other reasons. This shows that many have aspirations with the hope that market leadership is not yet firmly set. The products fall into the following: PCI-E SSDs (Fusion-io, LSI, Virident) SSD SAN (Violin, TMS, Whiptail) SSD caching (LSI, GridIron) I am inclined to be of the opinion that SSD market is not...(read more)

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• Queries barely over the Cost Threshold for Parallelism

  - by jchang

  I had discussed SQL Server parallelism in Oct 2010, with my thoughts on the best settings for: Cost Threshold for Parallelism (CTP) and Max Degrees of Parallelism (MAXDOP) in Parallelism Strategy and Comments . At the time, I had intended to follow up with detailed measurements. So now a mere 2 years later, here it is. The general thought was that CTP should be raised from the default value of 5, and MAXDOP should be changed from unrestricted, on modern systems with very many cores, and most especially...(read more)

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• HealthCare.Gov Fiasco

  - by jchang

  There will probably be consequences for delving into such a charged topic. But this has never stopped me before and I am too old to change my ways. So here goes. Many of us have of the problems with the online HealthCare.gov even though technical details are not yet available. First let me say that I am not singling out this particular project, as severe problems are common in government IT projects, and I suspect the incidence rate may be no different in private industry. Whereas other projects...(read more)

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• Queries barely over the Cost Threshold for Parallelism

  - by jchang

  Previously I had discussed SQL Server parallelism, with my thoughts on the best settings for: Cost Threshold for Parallelism (CTP) and Max Degrees of Parallelism (MAXDOP) in Parallelism Strategy and Comments . At the time, I had intended to follow up with detailed measurements. So now a mere 2 years later, here it is. The general thought was that CTP should be raised from the default value of 5, and MAXDOP should be changed from unrestricted, on modern systems with very many cores, and most especially...(read more)

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• Detecting Hyper-Threading state

  - by jchang

  To interpret performance counters and execution statistics correctly, it is necessary to know state of Hyper-Threading. In principle, at low overall CPU utilization, for non-parallel execution plans, it should not matter whether HT is enabled or not. Of course, DBA life is never that simple. The state of HT does matter at high over utilization and in parallel execution plans depending on the DOP. SQL Server does seem to try to allocate threads on distinct physical cores at intermediate DOP (DOP less...(read more)

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• New Seagate SSD and Hard Disks

  - by jchang

  Seagate today announced a near complete overhaul of their enterprise product line. This include second generation SSD now with either SAS and SATA interfaces. The first generation Pulsar SSD only supported SATA interface. The new 2.5in 15K and 10K hard drive models have higher capacity. The 2.5in 7.2K hard drive was upgraded to 1TB last month? The 7.2K 3.5in is now available upto 3TB. All models support 6Gbps. The new second generation Seagate Pulsar SSD comprises two product lines. The Pulsar XT.2...(read more)

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• Load Test Manifesto

  - by jchang

  Load testing used to be a standard part of the software development, but not anymore. Now people express a preference for assessing performance on the production system. There is a lack of confidence that a load test reflects what will actually happen in production. In essence, it has become accepted that the value of load testing is not worth the cost and time, and perhaps whether there is any value at all. The main problem is the load test plan criteria – excessive focus on perceived importance...(read more)

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• LOB Pointer Indexing Proposal

  - by jchang

  My observations are that IO to lob pages (and row overflow pages as well?) is restricted to synchronous IO, which can result in serious problems when these reside on disk drive storage. Even if the storage system is comprised of hundreds of HDDs, the realizable IO performance to lob pages is that of a single disk, with some improvement in parallel execution plans. The reason for this appears to be that each thread must work its way through a page to find the lob pointer information, and then generates...(read more)

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• Detecting Hyper-Threading state

  - by jchang

  To interpret performance counters and execution statistics correctly, it is necessary to know state of Hyper-Threading. In principle, at low overall CPU utilization, for non-parallel execution plans, it should not matter whether HT is enabled or not. Of course, DBA life is never that simple. The state of HT does matter at high over utilization and in parallel execution plans depending on the DOP. SQL Server does seem to try to allocate threads on distinct physical cores at intermediate DOP (DOP less...(read more)

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