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seperate drives for data-log even in VM envonrment

Posted on 2011-09-19
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Last Modified: 2012-05-12
in physical server for SQL Server database implementation, it is generally recommended to have data and log in separate drive (with separate spindles?)

is that standard applicable to Virtual servers also?
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Question by:25112
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Anuj earned 600 total points
ID: 36564774
Yes, you should reside in independent disk, this is applicable to tempdb also. These are best practice recommendation from Microsoft, The following link will help you regarding VMware best practice.
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by:Daniel_PL
Daniel_PL earned 600 total points
ID: 36564867
Independent disk (or group of disks e.g. in RAID) means that you should use different physical devices or groups of them for each type of files. This is because log files presents different I/O characteristic than data file(s). Log is written to as sequential unlike data files, which tends to be written in random fashion. In simplistic terms in an OLTP database, your throughput is determined by the speed of writes to the Transaction Log.
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by:Marten Rune
Marten Rune earned 600 total points
ID: 36565176
However there is a ongoing discussion about this, the concerns are data security (i e what data is at risk when XXX failes) and performace of the system.

The discussion goes like, if I set up a raid 5 for data, raid 1+0 for system, raid 1+0 for tempdb, raid 1+0 for logfiles and finally a raid 1+0 for indexes.

Will this genereate a faster more redundant environment than:

A Huge raidset perhaps raid6 with 19 spindles?

The above example with raid 5 and raid 1+0 has 19 spindles. The recommendations vary and really you will only know if you test your system, under similar pressure as expected to really know whats the best in every case.

In order to secure data, a raid6 can afford to loose two drives at once and it will still deliver, this is however not the case with the traditionally built system above. If the wrong two drives fail the server stops.

Sooner or later a system thats built on XXX Spindles will outperformance the traditionally built system, and be as secure or even more secure. The question in the debate is how to calculate the magic amount of spindles. This calculation also includes processors/cores, memory, and the behaviour of the system it's designed to support. So as always the answer is, it depends!

Regards Marten
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by:VENKAT KOKULLA
VENKAT KOKULLA earned 200 total points
ID: 36573630
The reason the data file (mdf) and log file (ldf) should normally be on separate drives is that when you’re doing inserts/updates/deletes, they both have to write at the exact same time.

It doesn't matter it's a virtual or physical server as i guess...
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by:25112
ID: 36576987
good info
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