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SAN and Disk Configuration Notes
 
This is just random thoughts on disk subsystems, SANs, and SQL.  See the attached ppt (right click and choose Save As) for some of this information based on a seminar I gave. 
 
What is a SAN?
At its simplest it is a collection of FibreChannel switches operating together as a fabric allowing servers and storage devices to communicate with each other using block protocols.  Sounds simple...and it should be.  But as we add many switches, with storage from different vendors, with different protocols, we realize that SANs have gotten complex...similar to how servers have gotten complex.  This complexity is a management nightmare, which has led to the advent of Virtualized SANs.  
 
General Disk Topics Storage Networking Technologies SAN Topics Other Items
 
Solid State Drives    
Dynamic Disks    
       

 

Storage Virtualization Peformance Useful Links
This is a hot topic in the trade rags since maybe 2007.  This is usually achieved via nodetitle or volume management software.  
When dealing with storage performance your two main concerns are bandwidth and latency. 
 
Here are some random performance thoughts for a database wired to a SAN:
  • Change RAID 5 to RAID 10
  • Utlilize a large stripe size
  • use a 64KB cluster size
  • 50% of your cache (or even more) should be for write-caching
  • for partitions > 2 TB do not use basic disks, use GPT drives
  • Consider having data files of equal size.  SQL Server's proportional fill algorithm might cause a file hotspot otherwise.  
  • Pre-size data and log files (using instant file initialization) where possible.  
  Latency and IOPs  
  SAN Performance Troubleshooting http://storageperformance.org
 
   
   
  Thin Provisioned Storage  
  SAN and Storage AntiPatterns  



 

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