11-04-2013 09:02 AM
Can someone confirm my understanding of CNFS in that clients can acces the same share from different nodes in the CNFS cluster.
So for example suppose you have 3 nodes, A, B and C and filesystem "/myshare" which is CFS mounted on all nodes and NFS shared on all nodes, then you could have 3 failover servers each containing a VIP - VIP1, VIP2, VIP3.
Then:
Client 1 can access /myshare via VIP1 running on Node A
Client 2 can access /myshare via VIP2 running on Node B
Client 3 can access /myshare via VIP3 running on Node C
If node C fails then VIP3 may fail to Node A and then clients 1 and 2 would both be accessing share on Node A, but by different VIPs
This is my understanding, but the example in the 5.1 CFS admin guide only shows 1 VIP service group which means in the example, there is no concurrent access of the share which I thought was the point of CNFS, or is the point of CNFS that you don't have to unshare and share when you fail over as shares are always there but there can only be one VIP for the share?
Mike
11-07-2013 11:40 AM
Mike,
There is (or should be) only 1 VIP for each CNFS service. The VIP is bound to each public NIC so each server in the CNFS cluster can handle requests. CNFS is a stateless application so each NFS request can be on a different node in the cluster. For example client 1 may be accessing a file on /myshare on node A but when the next file is accessed the request may be on node B.
You can read a bit more in the CNFS whitepaper here:
Before NFS clients connect to the CNFS server, the server’s virtual host name and IP address must be registered in the DNS server. The clients connect to any of the CNFS servers using the virtual IP addresses. By using DNS to direct clients to the CNFS cluster, the clients are load balanced between all the nodes of the CNFS farm. The load balancing is taken care of by DNS and typically employs a round-robin mechanism to do so.
11-08-2013 01:41 AM
I still don't understand if you are supposed to have one or multiple Virtual IPs (VIPs) - you say one VIP, but then in your post you use "virtual IP addresses" in the plural as does the white paper, which more explicity says " list of virtual IP addresses". i.e. you cannot round robin with one VIP so you must have more than one VIP.
Here is my understanding:
Before CNFS was available, you could only share a given CFS filesystem from ONE node at a time and so you had to use ONE VIP, so you had one service group (SG) containing that VIP and this service group could fail between SFCFS systems without having to import diskgroups and mount filesystems - and this is backed up by SFCFS admin guide (5.1) which says:
In previous releases, the SFCFS stack only allowed an active/passive setup forNFS serving due to the complexity of lock reclamation in an active/active configuration
My understanding of CNFS is that you can share a given filesystem from multiple nodes at the same time and therefore to access from mulitple nodes, you need multiple VIPS, each in its own service group and this is backed up by SFCFS admin guide which says:
This Clustered NFS feature allows the same file system mounted across multiplenodes using CFS to be shared over NFS from any combination of those nodes
11-25-2013 02:40 AM
Is anyone able to answer this - in essence the example in the 5.1 CFS admin guide shows one VIP service group (SG) and I thought the whole point of CNFS is that you could have 2 VIP SGs, so that you can access the NFS share from both nodes at the same time.
You can have 1 VIP SG with normal CFS + NFS, and if you can only have 1 VIP service group with CNFS, then the only difference between CNFS and CFS + (normal) NFS would seem to be that the share resource is in failover group for CFS + NFS, but in parallel group for CNFS.
Below is VIP SG in CFS Admin guide example:
group vip1 (SystemList = { system01 = 0, system02 = 1 }AutoStartList = { system01, system02 }PreOnline @system01 = 1PreOnline @system02 = 1)IP vip1 (Device = bge0Address = "10.182.111.161"NetMask = "255.255.252.0")NIC nic1 (Device = bge0)requires group cfsnfssg online local firmvip1 requires nic1