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Place system and data files on the salme disk Expand / Collapse
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Posted Friday, August 23, 2013 10:10 AM
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Hi,

Our DBA is currently installing a SQL cluster attached to a SAN. In order to optimize disk space usage, he informed us that he will be placing the database data files on the same disk where system files are stored. Log files are placed on a separate disk.

Is it a good idea to place system and data files on the same disk ? Will there be any performance issues ?

Thanks
Post #1487913
Posted Friday, August 23, 2013 3:21 PM


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My preference is to have tempdb on a separate disk, as there can be some quite heavy action in tempdb. If master, model and msdb are on the same disk as the data files is less of a concern.

Of course, since it is a SAN, there is a risk that it is all the same disk anyway, all depending on how the LUNs are carved out.


Erland Sommarskog, SQL Server MVP, www.sommarskog.se
Post #1488028
Posted Wednesday, September 11, 2013 11:14 AM


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SANs are a completely different animal. And even the variation in manufacturer and model change the "best practice" of how to lay out your files. The best thing to do is consult with the SAN vendor. At the very least, ask for their white paper or best practice documentation on how to lay out files for SQL Server. Any respectable SAN vendor will have this and be happy to share it with you.

Francis
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Post #1493814
Posted Thursday, September 12, 2013 9:53 AM
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Ask, and be very specific, what your SAN admin means by "disk".
Remember, you have, in some ordering (ask your SAN admin)

Physical spindles/SSD's

RAID groups

LUNs

MetaLUNs (sets of LUNs in a RAID)

For SQL Server performance, you need to know, at a minimum:
1) Which parts of which physical spindles/SSDs does each of your drive letters/mount points map to?
2) What else maps to those physical spindles/SSDs?
Post #1494259
Posted Friday, September 13, 2013 10:31 AM
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Not a very good idea if you are considering future performance and other DR deployement .

If your SAN admin is creating different mount points in the drive then the story will be different .


C:\ system files

D or E:\ SQL data file

M:\ Data files

L:\ Log files

T:\ Temp files
Post #1494660
Posted Friday, September 13, 2013 1:32 PM


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Um, NO! not good...

C:\ - OS only
E:\ - Apps - install of sql, various third party if any, ever
M:\ Mdf files - Data files
L:\ ldf files - only logs
T:\ tempdb - only temp
S:\ system databases - msdb, model, master


I know there can be different types of san, disk, mount points, but it is always good to have structure and best practice.


MCSA SQL Server 2012
Post #1494708
Posted Wednesday, September 25, 2013 1:27 PM


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I would like to add my 2 cents:
Whenever I can, I recommend against more than drive letters C and D and advice to use mount points for everything. It’s hard to make sure all servers have the same disk layout (in fact rarely ever) – especially when it comes to test and dev environment. I will spare you a list of advantages here.
Second: for most SANs and environments in general it nowadays does not harm to put tempdb on the same drive as the other databases. In fact it’s mostly better (more disks). And only if tempdb becomes a bottleneck, then I would move it to a dedicated LUN/Raid-Group.

Of course, as usual, this is also a matter of personal preference and (bad) experience.


Andreas

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MVP SQL Server
Microsoft Certified Master SQL Server 2008
Microsoft Certified Solutions Master Data Platform, SQL Server 2012
www.insidesql.org/blogs/andreaswolter
www.andreas-wolter.com
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