Direct SAN and stun

Availability for the Always-On Enterprise

Direct SAN and stun

Veeam Logoby JoshuaPostSAMC » Wed Nov 02, 2016 8:41 pm

I've been going down the road to change from virtual proxies to a physical proxy with Direct SAN, because I'm trying to reduce/eliminate the stun issue with large active VMs when a backup finishes, such as our SQL servers that can cause a failover

In the Best Practice guide I saw this line that made me look closer at this method:
https://bp.veeam.expert/resource_planni ... t_san.html
Direct Storage Access for NFS datastores will mitigate the "VM stun" issues that may be caused by Virtual Appliance Mode (hot-add).

I thought this meant it had a way to backup without a snapshot, as it is always when the snapshot is being removed that the stun occurs for us. I just ran my first test today and vCenter still placed a snapshot and removed it at the end, but there were new entries I had not seen before "Map disk region" and "Release disk lease".

What is the VM Stun issue with hot-add that was mentioned and how is it different than just a standard snapshot delete?
JoshuaPostSAMC
Expert
 
Posts: 116
Liked: 16 times
Joined: Thu Jul 30, 2015 7:32 pm

Re: Direct SAN and stun

Veeam Logoby sanjaykrk » Wed Nov 02, 2016 9:58 pm

Joshua,

Are you using Direct SAN or Direct NFS?

This is some description you might find useful.
While backing up a VM, any 'new' writes to the VM goes to a delta file. The original VM disk(s) is marked read-only for backup. This is how snapshot works.
Once backup is done, snapshot is removed (basically merge new writes ie. delta files with the VM disks. If these delta files are large (lot of writes while backup was being taken), merging with original disk can take long and may disrupt your activity on VM. This is 'stun'.

Now if you are using 'Backups using storage snapshot', it utilizes the SAN storage's capability to take snapshot and freeing up your actual VM disks quickly (resulting in small delta files and hence small merge time).

In short, snapshots will be taken for backups whichever transport mode you choose. Also this 'backup using storage snapshot' is independent of Transport mode. Direct SAN/NFS helps in keeping your Hypervisor (ESXIi) resources free and let the 'backup data' path avoid going through ESXi.
sanjaykrk
Influencer
 
Posts: 11
Liked: 3 times
Joined: Sat Apr 09, 2016 12:12 am
Full Name: Sanjay kumar

Re: Direct SAN and stun

Veeam Logoby JoshuaPostSAMC » Thu Nov 03, 2016 4:02 pm

I am doing Direct SAN.

I think I get it now. I saw zero impact to hosts and VMs and got excited about being able to avoid the stun issue on my SQL and Exchange servers, but now I see it is zero impact on Networks, since it happens outside of the host. I also missed that in the quote "Direct Storage Access for NFS datastores will mitigate the "VM stun" issues that may be caused by Virtual Appliance Mode (hot-add)." it was only for NFS so not applicable to me.

I'm not using Storage Snapshots. I am using a CIFS for my repository and the gateway server is my virtual B&R server, so all of the traffic would be coming back into the ESX network anyway. Add on that my ESX servers are in a Cisco UCS with 10 G network, and the physical proxy I'm testing with has only a dual 1 GB network, it looks like I'll be abandoning this plan and stick with my virtual proxies.
JoshuaPostSAMC
Expert
 
Posts: 116
Liked: 16 times
Joined: Thu Jul 30, 2015 7:32 pm

Re: Direct SAN and stun

Veeam Logoby dellock6 » Fri Nov 04, 2016 7:10 am

What vSphere version are you using? There have been large improvements in 6.0 in regards to snapshot commit, I wouldn't say the remove the issue of the stun, but it's largely mitigated, and more importantly this enhancement is independent from the backup method that is used, as it's directly related to snapshot technology. If this is not enough, the other options are indeed backups from storage snapshots, or to look at new technologies like vsan or vvols, that have a completely different snapshot mechanism.
Luca Dell'Oca
EMEA Cloud Architect @ Veeam Software

@dellock6
http://www.virtualtothecore.com
vExpert 2011-2012-2013-2014-2015-2016
Veeam VMCE #1
dellock6
Veeam Software
 
Posts: 5047
Liked: 1330 times
Joined: Sun Jul 26, 2009 3:39 pm
Location: Varese, Italy
Full Name: Luca Dell'Oca

Re: Direct SAN and stun

Veeam Logoby JoshuaPostSAMC » Fri Nov 04, 2016 1:19 pm

Still on 5.5 now until we finish upgrading our Citrix infrastructure and then we can move to 6.x

We don't have Veeam Enterprise Plus, so no storage snapshots for now.
JoshuaPostSAMC
Expert
 
Posts: 116
Liked: 16 times
Joined: Thu Jul 30, 2015 7:32 pm

Re: Direct SAN and stun

Veeam Logoby dellock6 » Fri Nov 04, 2016 10:46 pm

Ok, but the jump forward in snapshot management in vsphere 6.0 could potentially help you. We did some tests and these are the results:

http://www.virtualtothecore.com/en/vsph ... hing-past/
Luca Dell'Oca
EMEA Cloud Architect @ Veeam Software

@dellock6
http://www.virtualtothecore.com
vExpert 2011-2012-2013-2014-2015-2016
Veeam VMCE #1
dellock6
Veeam Software
 
Posts: 5047
Liked: 1330 times
Joined: Sun Jul 26, 2009 3:39 pm
Location: Varese, Italy
Full Name: Luca Dell'Oca


Return to Veeam Backup & Replication



Who is online

Users browsing this forum: Google Feedfetcher and 35 guests