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Is This Really a SAN Problem? Understanding the Performance of Your IO Subsystem

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Learn more about Embarcadero database tools at: http://www.embarcadero.com/products/database-tools

Nearly 80% of performance issues appear to be related to the performance of storage. In reality, only about half of those are actual bottlenecks - frequently things like missing indexes, bad database design or misuse of features can either negatively impact the performance of the storage, or make it look like the root cause of the issue.

Join Microsoft MVP, Joseph D’Antoni and Embarcadero Director of Software Consultants, Scott Walz as they shed light on diagnosing your IO subsystem.

In this session, you will learn:

+ Where to look in SQL Server to gather information
+ How to use Windows Performance Monitor to analyze storage performance
+ What a "false positive" storage problem might look like

There are only so many times you can yell at the SAN admin, before they get cranky and start giving you 1GB drives, so attend this session and learn when the time is right.

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Is This Really a SAN Problem? Understanding the Performance of Your IO Subsystem

  1. 1. EMBARCADERO TECHNOLOGIESEMBARCADERO TECHNOLOGIES Is This Really a SAN Problem? Understanding the Performance of Your I/O Subsystem Joey D’Antoni 16 September 2015
  2. 2. EMBARCADERO TECHNOLOGIES Joey D’Antoni • Joey has over 15 years of experience with a wide variety of data platforms, in both Fortune 50 companies as well as smaller organizations • He is a frequent speaker on database administration, big data, and career management • He is the co-president of the Philadelphia SQL Server User’s Group • MSCE, Business Intelligence, Database Administration • He wants you to make sure you can restore your data Joeydantoni.com
  3. 3. EMBARCADERO TECHNOLOGIES Agenda SAN and Storage Architecture The Language of the SAN Admin How SQL Server uses Storage Troubleshooting Performance Issues Summary
  4. 4. EMBARCADERO TECHNOLOGIESEMBARCADERO TECHNOLOGIES Poll Who Are You?
  5. 5. EMBARCADERO TECHNOLOGIES Bottlenecks
  6. 6. EMBARCADERO TECHNOLOGIES Memory versus Hard Drives
  7. 7. EMBARCADERO TECHNOLOGIES Storage Area Network
  8. 8. EMBARCADERO TECHNOLOGIES What is a SAN? Basically a specialized computer for storage Computer, Switches and Hard Drives Not a performance device Can be used for redundancy and DR purposes Will serve many servers—so critical piece of your infrastructure
  9. 9. EMBARCADERO TECHNOLOGIES SAN Components HBA (Fibre) Card—Connects your server to SAN via Fiber Optic cable iSCSI Card—Ethernet Card connecting server to SAN Switch—Either fibre or ethernet switch connecting server to SAN SAN head unit—Controls processing, RAID levels Disk Array—The physical array behind your SAN (a bunch of hard drives)
  10. 10. EMBARCADERO TECHNOLOGIES SAN Terms LUN—Logical Unit Number, but in practical terms, what your SAN admin will call a disk that he presents to your server Fibre Channel—Cable connection to SAN IOPs—I/O Operations Per Second—the way your SAN admin measures performance
  11. 11. EMBARCADERO TECHNOLOGIES Multi-Pathing How your SAN admin sleeps at night! Make sure your databases servers are multi-pathed
  12. 12. EMBARCADERO TECHNOLOGIES SAN Throughput 0 200 400 600 800 1000 1200 1400 1 GB iSCSI 4 GB FC 8 GB FC 10 GB iSCSI Max Mb/S Max Mb/S
  13. 13. EMBARCADERO TECHNOLOGIES Tiered Storage (Example—EMC VMax) Allows for dynamic moves of disk from faster to slower disks (Fibre channel to SATA), or slower to faster (FC to SSD) Totally dynamic, and seamless to servers Moves data in 768k extents Your SAN admin doesn’t know where your data is
  14. 14. EMBARCADERO TECHNOLOGIES FAST VP SSD SSD SSD 15K Fibre Channel 15k Fibre Channel 15k Fibre Channel 10K SATA 10K SATA 10K SATA Log Data
  15. 15. EMBARCADERO TECHNOLOGIES How to Tune a SAN Properly configure the array Spend lots of money
  16. 16. EMBARCADERO TECHNOLOGIESEMBARCADERO TECHNOLOGIES Poll How Frequently Do You Meet with Your SAN Team?
  17. 17. EMBARCADERO TECHNOLOGIESEMBARCADERO TECHNOLOGIES SQL Server and Storage
  18. 18. EMBARCADERO TECHNOLOGIES SQL Server Storage SQL Server uses 8k pages to store data Data is read page by page Data is written page by page Pages are grouped into 64k extents I/O patterns are mixed random and sequential Logical and Physical Reads
  19. 19. EMBARCADERO TECHNOLOGIES Large I/O Operations in SQL Server Checkpoints Scans Check DB Transaction Logging
  20. 20. EMBARCADERO TECHNOLOGIES Sequential Operations Transaction Log writes Backup Read-Ahead
  21. 21. EMBARCADERO TECHNOLOGIES Writing Pages to Disk Lazy Writing Eager writing Checkpoints
  22. 22. EMBARCADERO TECHNOLOGIESEMBARCADERO TECHNOLOGIES SQL Server I/O Demo
  23. 23. EMBARCADERO TECHNOLOGIES How to Monitor I/O in SQL Server • DMVs • Windows/Perfmon • Correlate Profiler/Perfmon
  24. 24. EMBARCADERO TECHNOLOGIESEMBARCADERO TECHNOLOGIES Poll How Do You Monitor Performance Over Time?
  25. 25. EMBARCADERO TECHNOLOGIESEMBARCADERO TECHNOLOGIES Perfmon Demo
  26. 26. EMBARCADERO TECHNOLOGIES What Perfmon Counters are Good/Bad for SQL and SANs • Avg. Disk Bytes/Read • Avg. Disk Bytes/Transfer • Avg. Disk Bytes/Write • Avg. Disk sec/Read • Avg. Disk sec/Transfer • Avg. Disk sec/Write • Disk Bytes/sec • Disk Read Bytes/sec • Disk Reads/sec • Disk Transfers/sec • Disk Write Bytes/sec • Disk Writes/sec • Split I/O/Sec • % Disk Read Time • % Disk Time • % Disk Write Time • % Idle Time • Avg. Disk Queue Length • Avg. Disk Read Queue Length • Avg. Disk Write Queue Length • Current Disk Queue Length
  27. 27. EMBARCADERO TECHNOLOGIES What to Look for in SQL Server Missing Indexes Queries with scans Page Life Expectancy It is very important to baseline this data—before and after are critical
  28. 28. EMBARCADERO TECHNOLOGIES 8 Tips for DBAs Baseline test your SAN before it gets loaded Baseline your SQL Server Performance Understand any changes in user workload through your baselines Work with storage team to understand your storage environment Be careful of SAN firmware upgrades Don’t blame the SAN until you have all of your data in place If performance is absolutely critical use local storage SANs, while cool, are not magic
  29. 29. EMBARCADERO TECHNOLOGIES Summary Learn how the SAN works, what it does and does not do Understand when and where SQL Server does its I/O SANs may not measure frequently enough Windows gives the best storage information You need to trend this data overtime to really understand your environment
  30. 30. EMBARCADERO TECHNOLOGIES Questions

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