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Category: Performance Tuning

Azure SQL Managed Instance Performance

Reitse Eskens wraps up a series on Azure SQL performance comparisons:

So far, the blogs were about the really SaaS databases; the database is deployed and you don’t have think about it anymore. This ease of use comes at a ‘price’. You’ve got no control whatsoever on files, you’ve lost the SQL Agent and a number of other features. The managed instance is a bit different. When I was testing you could see the TempDB files but not change them, since then a few changes have been made to this tier where you’re able to change settings and, Niko Neugebauer told the data community on twitter, there are more changes coming. With the managed instance, you get the agent back and you can run cross database query’s again. So you can safely say the managed instance is a hybrid between your trusty on-premises server and the fully managed Azure SQL database.

Click through for Reitse’s thoughts.

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RCSI and Blocking

Michael J. Swart says don’t worry, be happy:

What’s the best way to avoid most blocking issues in SQL Server? Turn on Read Committed Snapshot Isolation (RCSI). That’s it.

Do check out Erik Darling’s comment as well for one thing to keep in mind if you turn on RCSI.

The other thing to keep in mind is that, if you have WITH(NOLOCK) hanging around everywhere in your code, you won’t get as much of a benefit with RCSI until you remove them.

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Performance-Killing Pre-Emptive Waits

Sean Gallardy finds the real killer:

If you haven’t already read up on cooperative and preemptive scheduling or aren’t sure what those are, please read the intro to that first, otherwise you’ll be lost.

Much as I’ve discussed before, SQL Server uses a cooperative scheduling model. This doesn’t mean that Windows does, nor does it mean Windows will scheduler whatever SQL Server schedules, in fact much of the time there are many other threads that run before the ones from SQL Server, that’s the job of the operating system to figure out. Due to SQL Server using cooperative scheduling there needs to be a mechanism that exists such that when a resource not under SQL Server’s control needs interaction the scheduler can keep on scheduling and threads can switch in and out (in SQL Server, Windows does what Windows wants). Enter preemptive status and associated waits.

Click through for a deep dive on the topic.

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Troubleshooting I/O Issues in SQL Server

Ajay Dwivedi shares some advice:

Storage performance is something that puzzles a lot of SQL Server professionals. So in this blog, I will cover the basic steps I perform to ensure I get the best performance from the underlying storage.

Read on for some thoughts on storage testing prior to SQL Server installation, as well as what to do to ensure your SQL Server instance is up and at them.

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New Query Tuning Book

Grant Fritchey has a book for us:

If you’re interested in getting a digital copy, my brand spanking new book is now available here.

It’s in the intro, but let me tell you a little bit about the new book. It’s really new. Some of the older versions of the book were simply updated, a bunch of changes to most chapters, a couple of new chapters, fixes for old mistakes, ta-da, new book. Not this time. This time, I rewrote it all. From scratch.

Looks like I’ll need to get a copy.

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Performance Tuning Tables with Filters in Power BI

Chris Webb doesn’t want to wait:

There are four columns: Date, Town and two measures. One measure called [Fast Measure] is, as the name suggests, very quick to execute; the other measure, called [Slow Measure], is very complex and slow. The definitions are irrelevant here. Notice that there is a filter on this table visual so only the rows where [Fast Measure] is greater than 1 are shown.

If I measure the amount of time to render this table in Performance Analyzer, it takes around 17.5 seconds to run. However, if I remove the filter on [Fast Measure], the table only takes 8 seconds to run. Why? The filter is on the fast measure and surely more rows are returned without the filter, so wouldn’t the slow measure be evaluated more?

Click through for the answer.

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Diagnosing Kafka Message Throughput Reductions

Danica Fine and Nikoleta Verbeck troubleshoot an issue:

One of the greatest advantages of Kafka is its ability to maintain high throughput of data. Unsurprisingly, high throughput starts with the producers. Prior to sending messages off to the brokers, individual records destined for the same topic-partition are batched together as a single compressed collection of bytes. These batches are then further aggregated before being sent to the destination broker.

Batching is a great thing, and we (generally) want it. But how do you know when it’s working well and when it’s not?

This first post covers message throughput but there will be several other topics in the series as well.

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Parallel Loading of Tables in Power BI Dataset Refresh

Chris Webb hits the turbo button:

Do you have a a large dataset in Power BI Premium or Premium Per User? Do you have more than six tables that take a significant amount of time to refresh? If so, you may be able to speed up the performance of your dataset’s refresh by increasing the number of tables that are refreshed in parallel, using a feature that was released in August 2022 but which you may have missed.

Click through for that tip.

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Testing Azure SQL DB Hyperscale Performance

Reitse Eskens continues a series on performance testing Azure SQL DB tiers:

So far, my blogs have been on the different Azure SQL DB offerings where there are differences between DTU and CPU based. But in general, the design is recognizable. With the hyperscale tier, many things change. There are still cores and memory of course, but the rest of the design is totally different. I won’t go into all the details, you’re better off reading them here [] and here [] , but the main differences are the support of up to 100 TB of data in one database (all the other tiers max out at 40 TB), fast database restores based on file snapshots, rapid scale out and rapid scale up.

There are differences in testing this one versus the others, so buyer beware.

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Azure SQL DB GP Compute Optimized Performance Comp

Reitse Eskens continues a series on comparing the performance of different Azure SQL DB tiers:

The compute optimized tier starts at 8 cores as a minimum and goes up to 72.
The maximum storage starts at 1 TB and  goes up to 4 TB. The number of TempDB files is undisclosed but the size starts at 37 GB and goes up to 333 GB. A huge difference with the regular provisioned one! The disk limitations are disclosed as well. Log rate starts at 36 Mbps and maxing out at 50. The same goes for the data; starting at 2560 iops and maxing out at 12.800. One iop (or Input Output oPeration) is connected to the disk cluster size. As these are 4 kb, reading or writing one data page (8Kb) equals two iops. 2560 Iops equals something of 10 MB per second. The top end goes to about 50 MB per second. Keep this in mind when you’re working out which tier you need, because usually disk performance can be essential.

Read on to see how it performs on Reitse’s standardized test workload.

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