Solved

Microsoft SQL Server 2012 - Seperate drives for Logs and DB?

Posted on 2013-12-05
2
273 Views
Last Modified: 2016-11-23
Hi,

I'm just after peoples thoughts really.

All our MS SQL Servers are virtual machines.
Currently the VM's have two LUNS presented to them (iSCSI via Passthrough disks), one for SQL databases and the other for SQL logs
The LUNS all reside on the same group of Dell Equallogic iSCSI Arrays

Considering that the database and log drives both exist on the same storage arrays and on the same disks, is it worth having separate LUNS for databases and logs?

Performance is great with the current setup, so I don't see combining logs and databases on a single LUN will affect that.

We backup every 30 mins using Microsoft DPM

Any thoughts?
0
Comment
Question by:AJB_KRC
2 Comments
 
LVL 18

Accepted Solution

by:
Andrej Pirman earned 500 total points
Comment Utility
Your thoughts are correct.
Since it is same storage behind, the performance would not be better if you separate logs and DB on different LUNs. Maybe it is even better because using 1 LUN on iSCSI means iSCSI TCP encapsulation occures once, and for 2 LUNs twice, but I think it is unmeasured difference.
The gain would be if you would have LOCAL SSD disks, for example, in RAID1 config on server and use them for LOGS (as locally attached storage). RAID controller cache would help a lot, but that depends on your SQL Read/Write ratio in your usage scenario. IF you use, for example, 70/30 R/W average, then still 70% of performance would depend on reading from database (RAM and cache optimization helps a lot), and 30% are writes to file system (actually to RAID controller's cache).
So with local disks, this WRITE operation would happen faster and since MSSQL considers query done after it is written to LOG file (writing to DB happens afterwards and is not essential for performance!), this would improve some things.

So, in your current config I only see possible improvements in RAM and cache optimization for VM and of course, I hope you are NOT using MSSQL Express, rite? Express has 1GB RAM usage limit :)
0
 

Author Comment

by:AJB_KRC
Comment Utility
Thanks Labsy - we've started moving to single LUN's so we'll see how it goes!
0

Featured Post

What is SQL Server and how does it work?

The purpose of this paper is to provide you background on SQL Server. It’s your self-study guide for learning fundamentals. It includes both the history of SQL and its technical basics. Concepts and definitions will form the solid foundation of your future DBA expertise.

Join & Write a Comment

Let's review the features of new SQL Server 2012 (Denali CTP3). It listed as below: PERCENT_RANK(): PERCENT_RANK() function will returns the percentage value of rank of the values among its group. PERCENT_RANK() function value always in be…
Ever needed a SQL 2008 Database replicated/mirrored/log shipped on another server but you can't take the downtime inflicted by initial snapshot or disconnect while T-logs are restored or mirror applied? You can use SQL Server Initialize from Backup…
This video shows, step by step, how to configure Oracle Heterogeneous Services via the Generic Gateway Agent in order to make a connection from an Oracle session and access a remote SQL Server database table.
Viewers will learn how to use the INSERT statement to insert data into their tables. It will also introduce the NULL statement, to show them what happens when no value is giving for any given column.

728 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

14 Experts available now in Live!

Get 1:1 Help Now