Network Attached Storage: An Overview

By Bill Graziano on 11 July 2000 | Tags: Storage/Sizing

After last weeks article on NAS I thought we'd step back and give you an overview of what NAS is and what it can accomplish for you. We cover performance, capacity and a little pricing. These things aren't cheap!

Earlier we had an aritcle that discussed using Network Attached Storage (NAS) with SQL Server. We've had a number of questions about how NAS works so I thought I'd write an article.

Think of NAS as a giant disk drive that sits on your network. They are espcially usefull in situations where you have multiple servers on a network and want to consolidate storage. Network Appliance is one of the leading vendors of NAS and I linked to the following picture on their web site.

Their product is called a Filer. A Filer looks just like a file server to a client on the network. It can share files to either Unix or Windows clients. In this article we'll focus on the Windows side of the house. It can be managed just like a server using Server Manager. You can assign permissions to it just like you assign permissions on a Windows NT Server since it supports ACL's. You can also convince SQL Server that a Filer is really a local disk drive and create databases on it.

Their product is designed for maximum uptime and their web site boasts 99.999% uptime for the product. You can add disk drives on the fly without having to reboot. If you do need to reboot, the Filer comes back up in 2 minutes through a special file system that keeps a consistent data image on the disk. And of course, it's all RAID under the hood.

Performance
A Filer is connected to a SQL Server using Ethernet. Their base model (F720) boasts throughput of 124MBit per second. It does this using two 100Base-T network cards. In order for a single server to take full advantage of this throughput it would need comparable network capacity. And of course a switched 100Mbit Ethernet hub would be a good investment. At a minimum. Remember that a Filer is typically driving a number of SQL Servers as well as file sharing so it's network capacity should be much larger than any individual server.

Their high end model (F760) has a through put of over 235 Mbit per second using dual Gigabit Ethernet cards. And you can double that by clustering two of them! Putting these numbers into perspective 124Mbit/second is the equivalent of over 80 T-1 lines and 235Mbit is 156 T-1's. Their low end server has 256MB of RAM and their high end has 1GBof RAM. All this cache really helps to drive performance.

Capacity
Their low end model supports up to 464GB of storage and their high end model supports 1.4TB of online storage. So I'm sure you're asking what one of these babies costs. Network Appliances doesn't post prices on their web site but I have it on good authority that 350GB will run you roughly $250,000 if you buy it in two Filers. This works out to roughly $700/GB. That's not cheap folks. At that price an entry level filer will probably run you as much as $35,000 for 50GB. Actually probably less since your buying only a single device. Definely much more expensive than buying drives for a server but also much more flexible.

I also tried to check the Dell site for prices figuring I could price a quarter-million dollar NAS solution on-line. No such luck. Call for pricing. Compaq and EMC also sell this stuff. If you are using one of these, reply below and tell us how they work.