Network and Storage Protocols

FAS2020 design question



Please help me with the following questions because I have heard various opinions, but I cannot get a straight answer.

Basically I want to purchase a fas2020 primary for NAS purposes, but FC connectivity will be used too, so I need to clear this up.

If I have a FAS2020 active/active cluster with an additional DS14 SATA shelf, I should connect two FC ports, one from each controller (A & B) to the shelf.

The remaining two ports can be connected to a pair of Brocade FC SAN switches (SW1 & SW2). (controller A to SW1 & controller B to SW2 )

a. As far as I can understand, if the cfmode setting is single_image (which is the default), a host (eg. a Windows machine) that is connected to both switches can have redundant path to the storage by utilizing multipathing software. Is this correct?

b. If there is a tape library attached to SW1, can I use NDMP backup software (eg.Symantec Netbackup or HP Dataprotector) to backup the fas2020 data to the tape library through the FC connection, or is there any limitation such as that I cannot use tape libraries through FC, if the FC ports are already used for host connection to the storage (because of initiator/target mode of port) ?

c. If it is possible to utilize the tape concurrently with the host FC connection, should the SW1 and SW2 be connected to each other, or controller B will be able to access the tape library through the FC port of controller A which has the physical connection to SW1 where the library is connected?

d. If it is not possible, how can I send the NAS data to the tape? Is it possible to perform the backup through the LAN, but without mounting the filesystems from eg. the backup server? Will NDMP transfer the data through the LAN and send it to the Tape via eg. the backup server?





John -

a. Correct. With single_image cfmode the LUNs will be visible from both controllers all the time. Connection to the primary controller will be the primary (optimized) path and the second (failover) controler will be the secondary (non-optimized) path. Multi-pathing software is needed for cluster failover.

b. Correct - You won't have another initiator port (or set of ports) left to connect the tape drive with FC.

c. No, the tape drive would need to have connectivity to an initiator port.

d. Yes, you should be able to access the tape drive attached to the backup server through a network connection.

I hope this response has been helpful to you.

At your service,

Eugene Kashpureff
NetAppU Instructor and Independent Consultant
(P.S. I appreciate points for helpful or correct answers.)



thanks for your response. If it is possible can you clarify a few more things:

In question d, where the backups go through the LAN, the technology that is used is the "3-way NDMP backup" ?

In this case does the backup server need to mount the filesystems offered by the FAS2020 via NFS/CIFS, or all the data are accessed transparently using NDMP?

If I want to have multipath host FC access to the filer, while concurrently be able to perform NDMP backups to tape via an FC path, if I understand correctly, I have to use a different Netapp filer, so I should choose at least something like FAS2040 with SAS shelves?

Best Regards,




When you're using NDMP you're not mounting the volumes with CIFS/NFS. The filer sends the backup data out to a location under the direction of your NDMP-compliant backup software. Accordingly it's agnostic when it comes to protocols. In theory it is more efficient because the filer knows what data needs to be backed up, rather than your backup software having to stat every filesystem object over a NAS protocol. In practice don't expect it to be a speed daemon.

NDMP works a couple of different ways, you can get the filer to send the data directly to tape, or you can get it to send the backup stream to an NDMP storage server. Your backup software will likely support all of the available alternatives. We backup to the NDMP server rather than directly to tape, as we don't have an FC-based tape drive.

NDMP is really best thought of as a mechanism to allow existing backup suites to direct the filer to back itself up. Beware of the limitations, specifically that data which is backed up will be re-inflated if you have deduplication or compression enabled on your volume; and that if you're backing up SAN volumes ie iSCSI/FC LUNs then you can only backup the whole volume at once. Also watch out for the fact that NDMP doesn't do incremental backups. It does differential backups, so you may need to carefully configure your backup software to get the result you need. These are not really NetApp limitations but inherent limitations in doing file-by-file backups. The future lies in disk based backups, NetApp have a lot of technology to support this and they obviously would prefer you bought more of their kit to do things their way.

If your budget can be stretched up to the FAS2040 you should try to go for it. You'll have a lot more options, ie the option of ONTAP 8, SAS-based expansion shelves (which can also obviously take SATA and benefit from the inherent architectural improvements of SAS over a shared fibre channel link), more ethernet ports, lots more processing power/RAM/NVRAM.


Thanks for the info!  Everything seems clearer now!





you said two ports will be connected to the Switch. If the purpose is to run in target mode (possibility to present LUN's to a host), you can not use these connection for tape backup. If you just want to connect them to a FC Switch in case to be able to perform a backup (these ports run in initiator mode), your infrastructure will be fine.

I'm just asking because depending on your idea of how to use these Ports there is a "go" or "no go" for tape.