ONTAP Discussions

BD performance on LUNs v NFS



I have a question about the performance of running an Oracle database on a physical server verses a VM server. My DBA want a physical server as he feels performance would be much better, especially with disks holding lots and lots of files.  He wants to use iSCSI to LUNS on a NetApp FAS8020 instead of VMDKs on a NFS data store. My feeling is the performance difference would be negligible.  The network connection to the NetApp in either option would be 10GB.  I am looking for opinions for the two solutions.  If he would see better performance with LUNs over NFS or they would be about the same. I feel making it a VM guest with allocated resources would offer a better solution for many reasons. Part of his concern is the Linux CheckDisk funcition taking too long to run with NFS (10TB in 15 disks) taking over a day to run on all disks, he thinks LUNs would be quicker.


My recommended solution.

I talked with my NetApp engineer, about creating the storage my DBA wants for his new server. My DBA asked for 10 disks to be created. Five of them on the NetApp SAS disks, 1 TB each for a total of 5 TB of storage.  Five of them on the NetApp SATA disks, 1 TB each in size for a total of 5 TB of storage.  He also wanted to know if we be able to detach the disk from his new server and reattach them to either of the two existing VM guest v00hubdb-clone & v00hubdb-clone2 or vice versa.


If we used the s00Hubdb-new as a physical server moving the disks between it and a different physical server or virtual server and vice versa, as the DBA wants to be able to do, would be more problematical, at the file structure of the disks are different. If we made it a VM guest, moving the disk from one guest to another guest would be easy to accomplish.  So if moving the disks between servers is important having them all being VM guests, is the preferred method.


We talked about having the S00HUBDB-New as a physical server verses a VM Guest. If we took the server the DBA just finished with and used the VMware converter to do a P-to-V (physical to virtual) conversion it would make life and utility of this server much easier.  So if we used the VMware Converter, the DBA would not have to recreate the server.  We would convert it to a virtual, store it on the NetApp, then install VMware on the physical server add/regester the server (VM guest) to the new host, create and attach the drives, and it would be ready to go.  We could reserve or allocate the resources our DBA needs for that specific guest so it always has the resources he wants/needs for it.  As performance seems to be his biggest concern in wanting it to be a physical box.


If it was virtual we would be able to move it to a different host if the physical host needed maintenance or failed. We could still keep it running with a hit in performance, while the other host was being taken care of.  We would also gain all the normal VMware advantages also.


In talking with my NetApp engineer we could create either NFS shares or LUNs for this new physical server and the difference in performance would be negligible. However if we converted it to a VM and used the NFS shares we already have it would make moving the disks around so much easier. As we could just detach them from one server move the VMDK file the new server’s folder then reattach them to the new server.  We could use the same process to move them back if needed.


My DBA responded to the above proposal with the following and my NA engineer’s response in in italics.


I do not want to convert this into a VM host. I do not want to use vmdk files over an NFS link.


I want to move away from that method all together for certain Large volume drive mappings (drives with millions of files)


I need the NetApp devices to be able to be added to the s00hubdb physical box via the iSCSI hard disk setup.

Yes we can do this. We can create LUNs on NetApp and present them to a physical host or virtual guest host via iSCSI.


Lets just proceed with getting the 10 - 1 TB drives add. Thanks.


The other question I had about possibly moving one of those drives at a later point back to a current VM, ... is not a need, but rather a question I had about what was possible. The VMs have a full Linux install with the ability of having iSCSI attachments as well. From a technical standpoint this should be possible, but the VM guest would need access to the 10gb either. But this is not a need right now. It was an idea I had about giving back some of the space in use on v00hubdb-clone and clone2 at a later time, without having to spend tons of hours re-organizing files later on down the road. Its not worth wasting any more time on at this point. I will find another solution to this later on.


If I’m understanding this correctly we would have a LUN mapped to a particular Linux host “A”. Then later you may want to move this LUN to Linux host “B”. We can do this. You can dismount from Linux host “A” and then we unmap to Linux host “A” and map LUN to Linux host “B”.


We can also clone a LUN from Linux host “A” and then map the clone to Linux host “B”.


You Linux VM would just need to have an virtual adapter installed on the VM that is connected to iSCSI vlan.210. Currently the FAS8020 has two iSCSI LIFs (one on each node) that are on vlan 210.