SAN vs. NAS

2. More on SAN vs. NAS - FAQs

After I published my article "SAN vs. NAS - What are they and how do you manipulate them in Exchange" (please see below), I received a lot of feedbacks. Most of them are asking for opinions, I can't reply them one by one, so I publish them there:

 I.  Q: I am a network administrator and my main file server is almost out of disk space. There is no extra slot in the server so I can't put more hard disk in it. I have been looking for a solution until I saw your article. I believe the NAS is the right one I am looking for. Could you please tell me more technical details about it? Thanks a lot!

      A: If you are looking for just plain more disk space, NAS is the right solution. Let me use Dell 705N Snap Server as a example here ( I am not associated with Dell in any ways, they don't pay me. Its NAS is actually OEM of Quantum) as I am using it. You unpack it, mount it to the server rack, connect it to your switch via Cat.5 network cable, power it on. Wait 5 minutes, you will see a computer named "snapxxxx" in your DHCP server. It comes with built-in web interface, so you open your Internet browser, type in the "snapxxxx:, then you are prompt for a user name and password, you must be a Domain Admin to configure it. After you log in, you are in the Admin interface. Here you can do whatever you want - it is easy and self-explained - you can change the computer name, give it a IP address, create network share. The security model is very interesting: If you have access to the parent share folder, you have access to the children share folders; but if you don't have access to the parent share folder, you can still have access to the children share folders as long as you have the permission assigned.
       Then you can move some folders (particularly the Applications folder) from your file server to this NAS server and change your logon script, so users next logon, they are automatically pointed to the folders on the new server.

 II.  Q: I am a Exchange Administrator, I need a expandable space to put my Information Store. The SAN seems a right solution for my need. Can I put my Information Store in the SAN? What's your opinion?

        A: Yes, you can. But, I wouldn't recommend it. 

             At first, SAN seems really the good solution for Information Store - it is expandable, it is fast, it is reliable. The only problem is Microsoft does not explicitly announce to support SAN in its Exchange product. Remember what is SAN, it is a separate Network from your existing network, and as I mentioned in my previous article, it is still under developing. A major software company told me that they would announce a SAN support and management software at earliest in February, 2001. 

             Let's see what Microsoft does to manipulate SAN: they use SAN as on-disk backup and restore device for its Information Stores. 

             This is also my recommendation -- use SAN as your on-disk disaster recovery tool.

1. SAN vs. NAS - What are they and how do you manipulate them in Exchange

I was invited to a seminar about SAN and NAS a short while ago, I was amazed of how people misunderstanding it and trying to find which storage technology their companies should go. Let me explain something from my real working experience.

NAS, Network Attached Storage or Network Attached System. The name Network Attached Storage is preferred as it is more accurate. I call NAS is a "thin server", because basically it is a computer pre-configured as a server with a built in CPU, RAM, and a bunch of disks. It is a black box, which means it is not scalable - at least now. The good point of NAS is you can just plug it in and there, you have a big storage space in 5 minutes - I mean, really 5 minutes - you plug it to the network and power it on, within 5 minutes, you will find you have a new server on your network with a big hard disk. You don't need to configure anything, even not the ip address as it is pre-configured as DHCP. Of course you want to give it a ip address after if you wan it to be a server. Here is the spirit of NAS, simple. You want more storage space, here you go, plug it in, you have space now. It is cheap, the DELL 705N NAS server is Canadian dollar $5,000 with 240GB storage space. You can also configure it as RAID 5. So NAS, simple, easy, no new technology, no need any training, even the entry level guys can manage it, no headache - in my work experience, it is a little slow, which is understandable, it is a "thin server", remember? But this will lower your network performance.

So if you just need more storage space, go NAS.

How do you use it in Exchange? -- use it as a disk backup device. it provides faster backup and restore the tape. the new version of NTBACKUP, Seagate Backup Exec, CA Arcserve2000 all support backup to disk.

SAN, stands for System Area Network or Storage Area Network. Storage Area Network is more used. The key here is "network" -- it is a separate whole new network than your current network. It is a new technology you need put great energy and time into it. And it is still under developing, not too many support of it, which means if you want some free advices about it  from Internet, you could be disappointed and feel frustrated.  But it is great, it is a great technology. It means several servers can share one storage device. The center of the SAN is the Fiber Channel Switch. Fiber channel means it is fast - 1000megabits/second. Your servers connects to the switch via fiber channel card and fiber cable then connects to the storage space which is also a bunch of disks, via Fiber Channel Bridge. The SAN storage space is scalable and its access speed is fast. You normally want to put a fiber channel backup device in it then you can backup the servers in the SAN without consume network bandwidth. This will greatly increase your backup time and network performance.

So if you have money and need increase your network performance and need a scalable storage solution, go SAN.

How do you use it in Exchange? -- the same as NAS, use it a disk backup device. It provides great backup and restore speed, especially if you have a big Information Store, and/or you have a Service Level Agreement to provide a certain time to restore the IS.

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