Multiple VMs to Same iSCSI Target

[brupnick]

Good afternoon-

I should start by saying that my knowledge of iSCSI is elementary at best, but is it possible to present an iSCSI target to multiple VMs (two) on the same host? I have everything working as expected on VM1 on HOST4 (read/write), but I'd like to have VM2 on HOST4 also access the same target (as read-only).

Thank you!

Brian

[weinstein5]

Are you talking about the VMs accessing iSCSI targets form within the guest OS or store the virtual disks on the same VMFS datastore housed on the iSCSI LUN?

In either you actually can - 

[brupnick]

The VMs accessing iSCSI targets from within the guest OS (Windows Server 2008 R2 if it matters).

[weinstein5]

This will help you set up the MS iSCSI software intiator - http://technet.microsoft.com/en-us/library/ee338477%28v=ws.10%29.aspx

I am not sure how you can make it read-only

[brupnick]

I was able to get it connected using the iSCSI Initiator, but I'm not able to assign drive lettes to the drives. On my initial VM, I believe I'm using RDM, but am I correct that this configuration isn't possible on the second VM because I'm using it on the first?

[sparrowangelste]

brupnick are you using MSCS?

even if you are both win boxes will not be able to use the volume at the same time.

[brupnick]

No; they are all individual servers.

[markpattersones]

It simpler, easier to manage and more flexible if you just have the host access the iscsi target and create a datastore there then create a drive on that datastore for the virtual machine. Right now that is going to seem painful as you don't understand it but just read up on it a bit and you will have much better time in the future.

[brupnick]

A little context, just in case it helps. VM1 is a Veeam Backup and Replication server that's responsible for backing up all the VMs in my environment. The disk target for the backup files is a Synology DS1511+. The Synology has two volumes of 10 TB each and both are presented as iSCSI targets to HOST4 (where VM1 lives). VBR runs on VM1 and is able to write to the Synology.

I have a requirement to go to tape, so I have a physical server running Backup Exec 2010R3. This is a physical Windows Server 2008 R2 that uses the iSCSI Initiator to access the data on the Synology so that it can write the backup files to tape once a month (this is read-only access since it never should change the source files).

I replicate the VBR backup files to a matching Synology at our DR site via rsync. The problem is that when I run my full backups, the VBR jobs and the rsync replication end up running at the same time and crush my VBR server (VM1). My goal was to move the replication load to a second VM (VM2) so that VM1 would handle the backups and VM2 would handle the replication.

Because there's a physical server in this equation, I don't think I can do what Mark suggested, but please correct me if I'm wrong.

[markpattersones]

Just because VBR makes the files doesn't mean it has to replicate  them. Get the Synology to replicate your backup repository to the other  Synology.

I'd personally prefer to iscsi at the host level and then the vms are just presented with a datastore. It doesn't matter that you have a physical server here. Iscsi will still be communicating to the Synology just at the host level not the vm level. Getting used to this configuration means if you change storage systems you only need to change it once and also have more granular control of datastores.

Not sure about your read only requirement though.

[brupnick]

I don't even want to tell you how long I spent trying to get the rsync replication to run directly between the two Synology units. The problem is that there's no way for me to trigger the replication from Synology to Synology from the VBR server. Even after contacting support, the only way to do it is with a scheduled job on the Synology NAS, but the backup window can be 8 hours during the week and 24 when I run my fulls. The best solution for me was to put cwRsync on my VBR server and run the replication as a post command in the VBR job.

Please excuse the simple question, but if I present the iSCSI target to the host and then to the VMs as a datastore, how can I also get my physical server to see it? My guess is that I'd still have to use the iSCSI Initiator on the physical server.

As for the read only requirement, that's handled by the Synology GUI. When configuring the iSCSI mappings, I'm able to specify which connects are read/write and which are read only. I'm thinking out loud here, but if that's the case, could I present it to one host as read/write and to a different host as read only and just have my VMs live accordingly? I know that having multiple servers with read/write access can be problematic.

[mcowger]

You CAN present it that way, but it will be unlikely to work the way you hope.