• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 423
  • Last Modified:

Large Database on virtualized SQL server 2008 (vmware)

Industry experts seem to say that large databases (>500-800GB) should be placed on Raw Luns. Why? What happens if you just use a VMDK?
0
Johnjaysmith
Asked:
Johnjaysmith
  • 2
  • 2
  • 2
  • +1
5 Solutions
 
mcv22Commented:
Using virtualization of any kind has a performance overhead. If performance is not a concern, virtual disks should suffice.
0
 
JohnjaysmithAuthor Commented:
So Raw Luns are not virtualized? What is their structure as opposed to a vmdk?
0
 
coolsport00Commented:
No...RDMs are pointers to LUNs... not actual virtual disks.

~coolsporr00
0
Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
bgoeringCommented:
If you have no reason to cluster your sql server with some other physcial or virtual host, there is not any reason to use rdms. However, when allocating LUNs for your vmdk files normal database considerations apply. For example I will allocate a RAID 10 LUN to my ESX servers, and place database log datasets there. I use RAID 5 for about everything else.

As of VMware 3.5 there is not much difference in performance between rdms and vmdk files.

Good Luck
0
 
JohnjaysmithAuthor Commented:
Your question implied to me that clustering a sql server requires or does better with rdms (raw lun)?
Can you create a raid array with an rdms disk format?
0
 
coolsport00Commented:
Again, an RDM is solely a "pointer file", nothing more. It "points" to LUN disks. So, to answer your question...yes. Your LUNs can be whatever RAID your SAN supports. RDM provides 'direct access' to your SAN, whereas a virtual disk (VMDK) is storage on a VMFS volume (datastore), which is more than likely a LUN on your SAN (but obviously doesn't have to be).

Hope that helps.
~coolsport00
0
 
bgoeringCommented:
Yes, if you have a requirement to build a cluster that crosses physical host boundaries, could be virtual to physical, or virtual to virtual if each instance is on a seperate esx host server, you will need to use rdms for any luns to be shared between the servers. The local OS disks can be vmdks.

Creating the lun would be a function of your storage, create a lun like you would for anything in whatever raid format you want. When you present your lun to ESX, instead of adding it as a datastore to ESX, create the rdm link in the database  server configuration.
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Keep up with what's happening at Experts Exchange!

Sign up to receive Decoded, a new monthly digest with product updates, feature release info, continuing education opportunities, and more.

  • 2
  • 2
  • 2
  • +1
Tackle projects and never again get stuck behind a technical roadblock.
Join Now