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Switching from NAS-based access to SAN

We have a Sun server (Solaris 7), two Dell servers (NT), and a Compaq 7000 (Exchange 5.5) plugged to a Network Appliance F820 with 1 TB at a 10/100 connection. Is it efficient to connect a SX300 Dell Fibre Channel box with Fibre Channel switches to those servers with redundant HBAs and put F820 aside, rather than look for F820 1 TB growth through 10/100/1000? Our budget is around $150,000. We're using external tape backup.

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I will assume that you are using the NetApp F820 in file serving (NAS) mode using either NFS or CIFS. Working from that assumption, the first thing to talk about when deciding to switch from NAS-based access (e.g. using the NetApp F820) to block- or SAN-based access using block storage via Fibre Channel switches is how you are accessing and using the data. (Note: If you are going to use a pair of HBAs, then plan on using a pair of switches for redundancy.)

If you are actually sharing data between the servers, then you will need to continue to have some level of file sharing or NAS capability. If all of your data is uniquely accessed from different servers (e.g. there is no data sharing) then block-based access might be a fit for you. Second, do you have any performance challenges today on your network (available bandwidth, latency) as well as enough free ports for port connections? Third, are you out of storage capacity space on the F820? Will you need to add more storage? You already have an investment in your NetApp F820, so you should at least consider enhancing that with additional storage capacity if performance is OK.

If your network is the bottleneck, are you economically able to upgrade that, either by adding another switch, VLAN segment, or changing interfaces from 10/100 to 10/100/1000 assuming your network is capable of supporting this? Assuming your servers do not need data sharing, you could add a pair of Fibre Channel host adapters to your servers connected to a storage subsystem like the Dell CX300 via a pair of Fibre Channel switches. If you are not able to upgrade your existing network infrastructure and that is where your performance challenges lay, then stabling a small Fibre Channel-based storage network would be an option that could coexist with your existing NetApp F820. You could then attach a shared tape library to the Fibre Channel-based SAN and use shared library backup management software for your backups. You also have the option of using an iSCSI-based solution if you do not need file and data sharing. Vendors including NetApp offer combined block- (iSCSI) and NAS-based systems that you may also want to consider.

My final comment on backup is that unless you have already selected a tape solution and backup management software, you should look at some of the backup appliances that support disk-to-disk-to-tape (D2D2T) backups working with various software, or with integrated software. I'm sure there are many vendors, resellers, and solutions providers that would love to talk with you to help you spend your $150,000 budget, so shop wisely.

This was first published in September 2004

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