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Problems Regarding SQL Server Installation

Posted on 2000-02-15
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Last Modified: 2012-05-04
It is recommended that while installation of SQL Server if there is any "Disk Caching Controller" then disable it.

First I don't understand this  "Disk Caching Controller" , Do they talk from Hardware perspective or from Sodftware Perscpective.

Also I want to know about this  "Disk Caching Controller" in detail if possible.

If there is any site?
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Question by:ShehzadMunir
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by:david_levine
ID: 2522447
The reason is most likely because SQLServer has it's own caching and wants to protect you in case of a failure. If for some reason, you have a disk failure or loss of power between when SQLServer thinks it physically wrote something to disk and the disk caching controller wrote something, you could lose those changes to the database.

Not a real big concern though so don't sweet it that much.

David
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by:vandamme
ID: 2524314
Usually, a "Disk Caching Controller" is referring to Hardware.  When applications write to your hard drive, these controllers try to optimize your write time by holding the information in a cache until it has a full page\sector\(whatever) to write.  This helps your I/O, but if you lose power you lose any data in this cache.  That's why SQL Server wants you to turn it off.  It includes mechanisms which keep track of what data is actually written to the drive.  The two could interfere with each other, and cause data loss.  That's why they want you to disable it.  But like David said, it's no big deal, especially if you keep current backups which all "GOOD" DBAs do...
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by:ShehzadMunir
ID: 2529952
Thanks a lot. It helped me out.
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by:david_levine
ID: 2530923
So give one of us the points so the question is closed out.

David
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by:ShehzadMunir
ID: 2545496
Adjusted points to 20
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by:wqw
ID: 2547817
ungrateful bastard?

(i'm a non-english speaking:-))
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vujos earned 20 total points
ID: 2558090
Hi,

Some starting points :

1) Disk Caching Controller is hardware
   tahat is usaly used in combination  
   with RAID controllers (like
   MYLEX, SERVERRAID, ADAPTEC, DPT and
   many more).

2) Quality of Disk Caching Controller
   is measured in quality of Caching
   algoritam and quantity of on board
   RAM.

3) One of the parameters to look for (
   in the database world is battery
   backup). If database server app
   writes data to the disk (via cache
   controller without battery backup)
   data is stored  initialy
   in the controller memory,and not
   physically written on to the
   disk. If the failure of the hardware
   heppened in that moment data loss
   and logical incosistency will occur.

4) In order to avoid this select
   /DISK controller that does not
   have caching controller built in
   or in the controller setting
   disable ("Write Back") cache and
   enable ("Write Trough") mode.

Good reading for this also Microsoft SQL Server Administrators Companion on the page 766 and 767 under "Error 605".

Hope this is the complete answer.
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