Re: KVM virtual machine and SAN storage with FC

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Hi Brett,

On my plan is as follows:

I have two machine (Server) that will host two VM each. One for database and one for application. Then the two machine will provide (Load Balance and High availability). My intention is that all application files and data file for the database should reside on the SAN storage for easy access and update.

Therefore the storage should be accessible to both VMs through mounting the SAN storage to the VMs. The connection between SAN storage and the servers is through Fiber Channel.

I have seen somewhere talking about DM-Multipath but i dont know if this can help or the use of VT-d if can help. I will also appreciate if you provide some links to give me insight of how to do this.

If you need more information, please let me know.

Regards
 

From: Brett Worth <brett.worth@xxxxxxxxx>
To: denis bahati <djbahati@xxxxxxxxxxx>; Discussion about the virtualization on CentOS <centos-virt@xxxxxxxxxx>
Sent: Wednesday, 3 July 2013, 8:40
Subject: Re: KVM virtual machine and SAN storage with FC

On 03/07/13 15:22, denis bahati wrote:
Is there any body got any experience on setting up a virtualized environment in which the vm's can access a fiber channel SAN storage connected to host? the host access the SAN through its own HBA, but the hba is not recognized inside the virtual machines. Please let me know the step to go through this.

How you use this storage depends on whether you plan to do migration from one server to another.

If you're not going to be migrating then you can just allocate the FC LUN to LVM volume group and carve off logical volumes for the KVM VMs to use.  These can then have meaningful LVM names in /dev/vg_(VG)/lv_(LV) that can be allocated to the VM. See system-config-lvm.

If you're planning to migrate between machines then the LVM solution is not going to work.  In that case then you might need to create volumes on you FC controller that will be seen as individual devices/luns on the host servers.  There is a consistent device name that can be used that appears under /dev/disk/by-id. This will be identical on any host servers that can see that volume.  This can be allocated to the VM and will be consistent for a migration.  Using this method requires careful management and meticulous documentation of which LUNs have been allocated to which VM.  The lun ids are not very user friendly.

We've also have good results with DRBD for times when you want to be able to migrate between machines but do not have a SAN.  You have to  allocate all the storage on each server but you gain by having a sort of backup.

Finally, I can recommend convirt as a good system manager interface.


Regards
Brett

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