2010-06-07 12:29 AM
I found these helpful documents on NOW:
They pretty much answered my questions, except for one...
... now that I have my NFS storage repository on a NetApp volume, and several guest OS running on that SR, how do I make crash-consistent snapshots on NetApp side?
I need consistency for SnapMirror replication.
2010-06-07 01:37 AM
Even if the various guest OS are running at the time? Don't I need to make those consistent as well, like SnapManager for VI does in VMware environment, so I can surely bring them up on the DR side in case of disaster?
2010-06-07 01:43 AM
You said “crash consistent”. When host crashes, there is no way to make on-disk content consistent, it is too late. Snapshot is the same – if your systems are able to recover from crash, they should be able to recover from snapshot.
With best regards
Senior system engineer
2010-06-07 02:18 AM
Sorry, I meant to say on-disk consistent... :-)
Just as SnapManager makes a VMware guest OS flush all it's data on NetApp - and then make a consistent snapshot, I suppose I need do the same with XenServer?
What's the easiest way to achieve that?
2010-06-11 01:54 AM
I read Citrix XenServer and NetApp Storage Best Practices (http://media.netapp.com/documents/tr-3732.pdf) and I found a nice explanation on SnapShot:
SNAPSHOT FOR VIRTUAL MACHINES ON NETAPP DATA ONTAP AND NFS STORAGE REPOSITORIES
Creating VM snapshots for those VMs whose VDIs are resident on the NetApp Data ONTAP SR utilizes the NetApp device Snapshot technology directly by invoking the Snapshot at the device level. This results in minimal resource usage on the XenServer host in terms of CPU and memory during the snapshot process.
The snapshot process for VMs using the standard NFS, iSCSI, and Hardware HBA SRs, however, do not invoke any NetApp device capability. It uses the VHD capability for its VDIs to allow chaining for the original and snapshot VDI to share common data. The original VDI proceeds to make its own changes in an isolated copy-on-write version, with the snapshot VDI being Read Only.
XenServer 5 provides a convenient snapshot mechanism that can take a snapshot of a VM's storage and metadata at a given time. Where necessary, IO is temporarily halted while the snapshot is being taken to ensure that a self consistent disk image can be captured. Snapshot operations result in a snapshot VM that is similar to a template. The VM snapshot contains all the storage information and VM configuration, including attached VIFs, allowing them to be exported and restored for backup purposes.
However, before I could test this - I ran into a problem with a seemingly easy NFS SR setup described on pages 42-47.
I followed all the instructions but when I try to attach the NFS export (share) that I created on NetApp side (step 10), after I enter it's path 10.10.10.10:/vol/XenServer_NFS_Storage and hit Finish button - I get an error saying "The storage repository is not available. Check settings and try again." I tried some vatiations but the result is the same.
Do you have some experience with connecting NFS SR on NetApp with XenServer?
2010-06-21 01:06 AM
It would appear that the solution is to make sure that security is set to unix on volume level as well, it's not enough that the NFS export's security is set to Unix style. My default security was set to NTFS and that's what probably caused the problem when I created the volume for NFS SR.
The TR-3732 document didn't mention that detail. :-)
So, it's either FilerView -> Volumes -> Qtrees -> Manage or use the qtree security <volname> unix command to set security style for respective NFS SR volumes.
If anyone else finds this usefull (correct) post a reply here.