NFS share on RDM

[AllBlack]

Hi there,

I had to come up with an interim design and I was wondering how future proof it is.

The idea is that the data is accessible by several VMs (web server nodes) if need be, however one node is fine for now.

I created a virtual RDM (1TB on SAN) and mapped it to my VM. It is formatted with ext3.

What I might need to do in the future is give other nodes access to this data.

So what I thought of doing is, when that need arises, is to share this RDM out as an NFS share and map additional VMs

to this share.

My question is what would be best solution:

-Leave RDM mapped to VM1 and create NFS share on it and map other webnodes to it? Would there be an issue with one node writing directly and others over share (i.e. locking, corruption)

-Map RDM to a dedicated NFS server and share out to all web nodes?

The main reason for RDM choice was that it needs to be flexible as we don't really know a final design at this stage. And the dedicated NFS server could be a hardware solution.

Any gotchas in regards to VMotion and RDM in this scenario?

Cheers

[habibalby]

Hello,

Present the RDM LUN to the ESX Hosts, and don't format them as ext3 "VMFS". Because you need to make the same lun "RDM" to another Node "VM". In here, just choose to be a Virtual Compatibality RDM instead of Physical in order get a VMotion,

Best Regards,

Hussain Al Sayed

[Texiwill · Accepted solution]

Hello,

What I might need to do in the future is give other nodes access to this data.

So what I thought of doing is, when that need arises, is to share this RDM out as an NFS share and map additional VMs

to this share.

This is the best solution as mapping an RDM to multiple VMs requires a clustered filesystem and ext3 is not a clustered filesystem.

My question is what would be best solution:

-Leave RDM mapped to VM1 and create NFS share on it and map other webnodes to it? Would there be an issue with one node writing directly and others over share (i.e. locking, corruption)

This is a good solution.

-Map RDM to a dedicated NFS server and share out to all web nodes?

I think this is a better solution as you can tune the NFS server independent of the web servers. Web servers and NFS servers often have different ways to tune things for optimal performance. Plus you can eventually use the LUN for a physical NFS server as well.

The main reason for RDM choice was that it needs to be flexible as we don't really know a final design at this stage. And the dedicated NFS server could be a hardware solution.

RDM is a great solution for this.

Any gotchas in regards to VMotion and RDM in this scenario?

Make sure the RDM is a 'virtual RDM' then you will have no issues. Physical could work, but virtual is better.

Best regards,

Edward L. Haletky

VMware Communities User Moderator

====

Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.

Blue Gears and SearchVMware Pro Blogs: http://www.astroarch.com/wiki/index.php/Blog_Roll

Top Virtualization Security Links: http://www.astroarch.com/wiki/index.php/Top_Virtualization_Security_Links

[AllBlack]

Thanks Edward,

I am glad to hear I came up with a good solution

However, I had already created this setup before submitting my post.

I did create the RDM as physical. Is there a way of reversing this to virtual without destroying the RDM?

I did not have a need for snapshots and physical supports vmotion therefore I made the physical choice.

Now this might be a silly question, Do other hosts in the cluster have to map to the RDM too (for DRS/HA) or

is access to the lun containing mapping sufficient?

Cheers

[Texiwill]

Hello,

I am glad to hear I came up with a good solution

I use something similar for one of my customers.... We are actually looking into cached clustered filesystems ala coda.

However, I had already created this setup before submitting my post.

I did create the RDM as physical. Is there a way of reversing this to virtual without destroying the RDM?

Yes just change it to Virtual under Edit Settings, no impact to the disk.

I did not have a need for snapshots and physical supports vmotion therefore I made the physical choice.

That works as well. Snapshots are used as a part of the backup process and I like to make backups of my data periodically.

Now this might be a silly question, Do other hosts in the cluster have to map to the RDM too (for DRS/HA) or

is access to the lun containing mapping sufficient?

Yes.

Best regards,

Edward L. Haletky

VMware Communities User Moderator

====

Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.

Blue Gears and SearchVMware Pro Blogs: http://www.astroarch.com/wiki/index.php/Blog_Roll

Top Virtualization Security Links: http://www.astroarch.com/wiki/index.php/Top_Virtualization_Security_Links