Indexing strategies and good physical designs for performance tuning Kenneth Ureña /SpanishPASSVC

Agenda  The journey of a transaction  Performance degradation factors  Physical Designs  Indexing  Coding best practices

THE JOURNEY OF A TRANSACTION

Actual empty Virtual Log File Truncated -Sequential Access -Just 1 file Active -Recommended Raid 1 ó Commit, backup log trigger I/O Log File -Random Access -Multiple datafiles Active -Recommended Raid 1/ / 5 -Checkpoint, backup, load / unload Cache FullEmpty FullEmpty Full EmptyFull Data Files Cache fail Loads page Update page Commit Lazy Writter / Checkpoint

PERFORMANCE DEGRADATION FACTORS

HardwareSoftware DB Performance Degradation life cycle Overload Degraded Performance CPU / Memory Storage Peripheral Database Data Algorithm

Sata, SAS, SSD (Types of Hard Drives) Big performance difference between Sequential IO vs Random IO IOPS (In Out Per Second) IOPS Estimated = 1 / ((seek time / 1000) + (latency / 1000)) Storage Reference

Average read seek time: 3.4 ms Average write seek time: 3.9 ms Average latency: 2.0 ms Seek time = ( Average read seek time + Average write seek time) / 2 = ( ) / 2 = 3.65 ms IOPS Estimated = 1 / ((seek time / 1000) + (latency / 1000)) = 1 / ((3.65/1000) + (2.0 / 1000) = ~ 175 IOPS SAS - 600GB 15K - Seagate Reference

Raids Raid 0 Raid 1 Raid 5 Raid 1 + 0

Raid 0 (Stripping)  Logical Drive Characteristics  IOPS = #Disk * IOPS Estimated  S ize = #Disks * Size disk  Pros  High performance  Low cost  Cons  Fault tolerance

Raid 1 (Mirroring)  Logical Drive Characteristics  IOPS = (#Disk / 2) * IOPS Estimated  S ize = (#Disk / 2) * Size disk  Pros  Fault tolerance  Cons  Higher cost

Raid 5  Logical Drive Characteristics  IOPS = (#Disk - 1) * IOPS Estimated  S ize = (#Disk - 1) * Size disk  Pros  Fault tolerance  Cost Effective  Cons  Recalculation on raid failure  Parity calculation

Raid  Logical Drive Characteristics  IOPS = (#Disk /2) * IOPS Estimated  S ize = (#Disk / 2) * Size disk  Pros  Fault tolerance  Cons  Cost

Database Files Random Access Multiple Actives Data File Sequential Access One Active Log File

PHYSICAL DESIGNS

Physical Designs Choosing the right Raid for the Database File Split the files in order to get the expected Access behavior

Scenario #1 1 User Database High OLTP Traffic High TempDB consumption 16 Cores Server

Scenario #1 (Proposal 1) Raid 1+0 Drive SAS TempDB UserDB Raid 5 Drive SAS Raid 1+0 Drive SAS LOG File Data File

Scenario #1 (Proposal 2) Raid 1+0 Drive SAS TempDB UserDB Raid 1+0 Drive SAS Raid 1+0 Drive SAS LOG File Data File

Scenario #1 (Proposal 3) TempDB UserDB Raid 1+0 Drive SSD Raid 1+0 Drive SAS LOG, Data File LOG File Data File

Scenario #2 multiple User Database High OLTP Traffic High TempDB consumption multiple Cores Server

Scenario #2 (Proposal 1) Raid 1+0 Drive SAS TempDB Raid 1+0 Drive SAS Raid 1+0 Drive SAS LOG File Data File UserDBN Raid 1+0 Drive SAS Data File Raid 1 Drive SSD UserDB1 LOG File

INDEXING

Indexes and Organization Table structure Image from SQL server 2008 books online

Indexes and Organization Heap Table Image from: SQL server 2008 books online

Indexes and Organization Clustered Table Image from: SQL server 2008 books online

Clustered (example) Image from:

Indexes and Organization NonClustered Index Image from: SQL server 2008 books online

Column Index Image from

Data access patters  Seek  Scan  Bookmark Lookup

Data access patters DEMO

CODING BEST PRACTICES

Coding Best Practices  Maximize coverage  Avoid conversions (implicit/explicit)  Avoid row by row access (cursor pattern)  Avoid unnecessary sorting  Choose the right index for the expected data pattern access method

Q&A Thank you Kenneth Ureña /SpanishPASSVC