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How to improve TempDB performance?

How to improve TempDB performance? 

1) TempDB file size and physical placement on harddrive can affect the performance of a system

2) Set the tempdb recovery model to simple 

3) Do the capacity planning of the TempDB database and pre allocate the appropriate size to MDF files, which will improve performance for allocating size 

4) Put TempDB on fast I/O System 

5) Create as many tempdb data files by considering the number of cpu 

6) make all the tempdb data file size same

Troubleshoot Suspect Database Issue

Problem

How to troubleshoot suspect database problem? How to bring it back online? What are the do you need to perform once the database is online?



Solution

Step 1: Bring the database online using below script

USE Master

GO

 

-- Determine the original database status

SELECT [Name], DBID, Status

FROM master.dbo.sysdatabases

GO

 

-- Enable system changes

sp_configure 'allow updates',1

GO

RECONFIGURE WITH OVERRIDE

GO

 

-- Update the database status

UPDATE master.dbo.sysdatabases

SET Status = 24

WHERE [Name] = 'SuspectedDatabaseName'

GO

 

-- Disable system changes

sp_configure 'allow updates',0

GO

RECONFIGURE WITH OVERRIDE

GO

 

-- Determine the final database status

SELECT [Name], DBID, Status

FROM master.dbo.sysdatabases

GO

Step 2: Check for database corruption. This is very important step please execute it.

• DBCC CHECKDB - Validate the overall database integrity


• DBCC CHECKCATALOG - Validate the system catalog integrity


• DBCC CHECKTABLE - Validate the integrity for a single table

Step 3: To resolve the corruption issue, please execute below commands

• Drop and Recreate Index(es)


• Move the recoverable data from an existing table to a new table


• Update statistics


• DBCC UPDATEUSAGE


• sp_recompile

Step 4: Repeat Step 2 to validate all the corruption occurred

DRBD, Heartbeat and MySQL

The easiest solution to implement clustering in MySQL is DRBD and Heartbeat.

DRBD: The Distributed Replicated Block Device (DRBD) is a software-based, shared-nothing, replicated storage solution mirroring the content of block devices (hard disks, partitions, logical volumes etc.) between servers.

DRBD mirrors data

• In real time. Replication occurs continuously, while applications modify the data on the device.


• Transparently. The applications that store their data on the mirrored device are oblivious of the fact that the data is in fact stored on several computers.


• Synchronously or asynchronously. With synchronous mirroring, a writing application is notified of write completion only after the write has been carried out on both computer systems. Asynchronous mirroring means the writing application is notified of write completion when the write has completed locally, but before the write has propagated to the peer system

You can download DRDB from below site

http://www.drbd.org/download/packages/

Memcached & MySQL

memcached (pronunciation: mem-cash-dee.) is a general-purpose distributed memory caching system that was originally developed by Danga Interactive for LiveJournal, but is now used by many other sites. It is often used to speed up dynamic database-driven websites by caching data and objects in memory to reduce the number of times an external data source (such as a database or API) must be read. Memcached is distributed under a permissive free software license. Memcached lacks authentication and security features, meaning it should only be used on servers with a firewall set up appropriately. By default, memcached uses the port 11211. Among other technologies, it uses libevent. Memcached's APIs provides a giant hash table distributed across multiple machines. When the table is full, subsequent inserts cause older data to be purged in least recently used (LRU) order. Applications using memcached typically layer memcached requests and additions into core before falling back on a slower backing store, such as a database. You can download memcached API from http://www.danga.com/memcached/