How to use paravirtual driver on Veeam server

[virtualwatts]

Our Veeam server is a VM and we use Virtual Appliance backup mode.

On each of our VM's the boot drive (0:0) is LSI and all other disk are paravirtual.

However, I've noticed that when Veeam hot adds drives for backup that it does so only using LSI, no hot adds use the paravirtual.

Is there a way to change that behavior?

Thanks
Rick

[Vitaliy S.]

Hello Rick,

I've done some search on paravirtual SCSI adapters and have found the following set of limitations:

Hot add or hot remove requires a bus rescan from within the guest.

Disks with snapshots might not experience performance gains when used on Paravirtual SCSI adapters or if memory on the ESX host is overcommitted.

If you upgrade from RHEL 5 to an unsupported kernel, you might not be able to access data on the virtual machine's PVSCSI disks. You can runvmware-config-tools.pl with the kernel-version parameter to regain access.

Because the default type of newly hot-added SCSI adapter depends on the type of primary (boot) SCSI controller, hot-adding a PVSCSI adapter is not supported.

Booting a Linux guest from a disk attached to a PVSCSI adapter is not supported. A disk attached using PVSCSI can be used as a data drive, not a system or boot drive.

Booting a Microsoft Windows guest from a disk attached to a PVSCSI adapter is not supported in versions of ESX prior to ESX 4.0 Update 1.

Sounds like you need to switch to network mode to make it work.

Thank you.

[virtualwatts]

Thank you Vitaliy -

It was just an inquiry. I knew about the conditions for using paravirtual but I guess I was thinking that in virtual appliance mode Veeam wouldn't have the same limitations. We cannot use SAN mode as we are a VM and Network mode was too slow to meet our window. We'll stick with para on the servers and LSI in Veeam for now.

Rick

[Moebius]

Bringing up an old topic.

So with ESX4.1 and a Windows guest Veeam server booting from a PVSCSI adapter, would the hot-added disks use the PVSCI adapter? And in this case, could performance improvements be expected?

Lucio

[Gostev]

According to the above (see in red), hot-adding a PVSCSI adapter is not supported.

[tsightler]

No, hot-adding is supported, as long as the system is booted from a PVSCSI adapter. Back in 4.0 U1 this was not supported, but I'm pretty confident that booting a Windows systems from PVSCSI is fully supported under 4.1. Assuming the boot disk is using PVSCSI, then PVSCSI will be used for all hot-added disk.

No, to be fair, I don't know if this will work with Veeam because PVSCSI requires a bus scan for hot added disk, but I think VMware tools takes care of this somehow.

[Moebius]

Ok, since I couldn't get a satisfactory reply from the Veeam guys, I decided to go on and try myself.

In ESX 4.1 U1, on a virtual Windows 2008 R2 Veeam server with PVSCSI as its boot and only adapter, the hot-adding method works without any problems. As Tom says, if the boot disk is using PVSCSI, then PVSCSI will be used for all hot-added disk.

However, I did not notice any performance improvements over the LSI SAS adapter.

[Gostev]

Thanks for the update, Lucio!