I’m sure that all of you know what a NAS device is, but in the unlikely event that you don’t, here is a good definition from Wikipedia:
“A class of systems that provide file services to host computers. A host system that uses network attached storage uses a file system device driver to access data using file access protocols such as NFS or CIFS. NAS systems interpret these commands and perform the internal file and device I/O operations necessary to execute them.”
Large organizations normally deploy storage area networks (SANs) to provide robust, scalable storage for their users, but smaller companies, which are just as dependent on uninterrupted messaging service as the large ones, can’t afford this expensive technology.
Windows Storage Server 2003 enables the use of NAS for applications, file serving, and since April 2004, with the release of Windows Storage Feature Pack, Exchange server.
The decision about which kind of storage to use for Exchange Server should not be taken lightly. There are many aspects you should consider, but, providing that you meet all the performance requirements, there may be some characteristics of NAS that may convince you to decide in favor of this technology:
- Flexibility: NAS devices with Windows Storage Server 2003 allow you to pool storage for application, file, and Exchange use. Consolidating storage from server-based DAS onto NAS makes it easier to allocate and reallocate storage as business requirements dictate.
- Cost-effectiveness: NAS is almost always cheaper than SAN on a per-megabyte basis. Besides, because storage costs can be amortized across Exchange and file services, economies of scale and consolidation of hardware combine to make NAS highly price competitive.
- Ease of deployment: NAS with Windows Storage Server provide seamless integration with Exchange and Active Directory. They can be managed and updated with the rest of your Windows infrastructure and they use familiar Windows tools and utilities, so you get reduced operational complexity.
The Windows Storage Feature Pack
If by now you are eager to put your hands on a NAS device and use it with Exchange, there are some things you should know first. The feature pack requires a Windows Storage Server 2003 server and a server running Exchange 2003. The Feature Pack must be installed on both the Windows Storage Server computer (NAS device) and the Exchange Server 2003 computer to add new components and functionality to each. These components provide tools and services that enable Exchange databases and transaction logs to be moved to a Windows Storage Server computer and to configure Exchange Server 2003 access to the remotely stored files.
Besides that, there are some recommendations and best practices you should follow when using it with Exchange:
- Disk configuration: For the best performance with Exchange, the feature pack server should be configured with an appropriate number of disks and appropriate interfaces. You still have to correctly size the disk subsystem according to your needs. In general, it is necessary to provide enough disk spindles to keep the average disk queue length and latency times within the acceptable values.
- Network connectivity: The Exchange 2003 and the NAS device should be interconnected with dedicated Gigabit Ethernet adapters and components. Low-capacity servers can be interconnected via a crossover cable; medium-capacity servers should be connected with a hub, and high-capacity servers will generally need a separate Gigabit Ethernet switch.
- Storage group configuration: With the Feature Pack installed, a Windows Storage Server computer supports as many as four storage groups from as many as two Exchange servers (Microsoft doesn’t recommend putting more than 2 storages groups on the NAS hardware). Unless you are using a high-capacity NAS server, you should place just one storage group on NAS, leaving the transaction logs on the Exchange server, as illustrated on Figure 1. This configuration physically separates the logs and databases onto separate computers, increasing the chances of a successful disaster recovery in case of a failure or disaster.
Figure 1: Typical Storage Layout for Exchange 2003 with the Feature Pack
For the purpose of this article I used an HP Storage Works NAS b2000 gently provided by HP Portugal, with the following configuration:
Figure 2: HP StorageWorks NAS b2000
- Intel Xeon 2.80 GHz Processor with 512-KB level 2 ECC cache
- 1 GB Standard PC2100 DDR SDRAM
- Integrated Smart Array 5i Plus Controller with optional Battery-Backed Write Cache
- 2 x NC7781 PCI-X Gigabit NICs (embedded) 10/100/1000 WOL (Wake on LAN)
- Internal storage: 1×36.4 GB Ultra320 10K drive (for OS); 2 x 9.1 GB Ultra3 10K (for user data)
There is no additional charge for the Feature Pack. A CD ships with the HP ProLiant Storage Server, which includes some Microsoft hotfixes, security updates, and the Feature Pack.
The setup process I’ll describe, although specific to the HP StorageWorks device, can be mapped to practically all NAS hardware, since the operations involved are basically the same.
The installation involves the following tasks:
- Ensure that installation requirements are met. Carefully read all the documentation that comes with the NAS hardware. HP provides very good documentation about the setup process, you’ll find a list of related links at the end of this article.
- Set up and configure a dedicated Gigabit network for Exchange database traffic. Although this is not actually a requirement, it’s strongly recommended that you do so.
- Edit the hosts files on the Exchange server and NAS Server computer to use the dedicated network. This is a very important step, because in case you forget this you’ll end up using the LAN interface for the database data flow. Be sure to add an entry in the hosts file of each server that points to the other machine.
Table 1: Sample HOSTS file
Windows Storage Server
IP Address of dedicated network
- Now it’s time to set up a dedicated volume on the NAS device. This is a regular NAS operation, it’s not exclusive of the Exchange setup process. If you use the NAS hardware for any other purpose, certainly you’ve done it before. Nevertheless, for those of you who aren’t familiar with NAS storage, this operation involves creating a volume and selecting the appropriate sharing protocols (Figures 3 and 4).
Figure 3: Configuring NAS Disks
Figure 4: NAS Sharing Protocols
- Install the feature pack on the Windows Storage Server 2003 server. This installation extends the Web UI component by adding a task for creating new shares for Exchange files (Figures 5 and 6) and it creates a share that holds the files to be installed on the Exchange 2003 server.
Figure 5: Creating a Share for Exchange
Figure 6: Creating a Share for Exchange
- The next step is to install the Exchange feature pack components on the Exchange server. The required installation binaries are located in the SMB share on the NAS device. There are 2 installation methods available: using command line or by running the setup wizard (Figure 7), being the late the easiest way.
The installation process installs the following components on your Exchange server:
- Windows Storage Server Mapping Service (WSSExchMapSvc). This service creates a mapped drive for use for Exchange shares on the remote storage servers each time the Exchange server or Windows Storage Server Mapping Service is restarted (Figure 8).
- The WSSExchMove command-line tool and the Remote Storage Wizard. These tools are used to move Exchange storage groups to and from a Windows Storage Server computer.
As part of the Exchange server configuration, the Microsoft Exchange Information Store service dependencies are modified so that the configuration depends on the Windows Storage Server 2003 Feature Pack Group, as shown in Figure 9. At this time, if you open Windows Explorer you’ll see a “Disconnected Network Drive”, that’s the NAS volume created previously and that will hold the Exchange databases (Figure 10).
Figure 7: Feature Pack Setup Wizard
Figure 8: Windows Storage Server Mapping Service
Figure 9: Dependencies of the Information Store Service
Figure 10: The NAS drive (S:)
Move the Exchange database files from the local server NAS. This operation is performed with the Remote Storage Wizard (you can also do it via the command-line tool WSSExchMove). On the Exchange server, start Exchange System Manager, open the Server container in the console tree, click the storage group with the databases that you want to move, point to All Tasks, and click Remote Storage Manager (Figure 11).
Figure 11: Initiating the Remote Storage Wizard
- The Remote Storage Wizard (RSW) is pretty straightforward. Start by selecting the type of operation you want to perform (Figures 12 and 13). The Full transfer option updates Active Directory and transfers the files to their new locations. During the move, the wizard dismounts the stores that are being moved (if you are moving log files, all stores are dismounted). After moving the files, it remounts the stores, so no further intervention is needed.
Specify the NAS device as the storage destination for the Exchange files (Figure 14) and select which folders will store the databases for this storage group (Figure 15). If Browse for Folder dialog box (Figure 16) does not list the shared folder that you want, make sure that the share has been created on the NAS computer and that Full Control permission for both the share and the underlying folder has been assigned to you and to the Exchange server.
Figure 12: RSW: Selecting operation to be performed
Figure 13: RSW: Selecting type of move
Figure 14: RSW: Server selection
Figure 15: RSW: File location selection
Figure 16: RSW: Browsing for folder
And that’s all it takes. If everything worked, you should now have the Exchange databases located on the NAS device. You can check the Mailbox Store properties (Figure 17) or browse the database files using Windows Explorer (Figure 18).
Figure 17: Mailbox store properties
Figure 18: Exchange database files
I was also curious to see the behavior of Exchange regarding performance when using NAS. So I downloaded the latest version of JetStress (yes, it now supports NAS) and did some quick tests.
For the purpose of this test I used the following scenario:
- 100 Mailboxes
- Average profile (0,5 IOPS/Mailbox)
- 50 Mbytes
Although I would like to test a heavier load using more users, I was limited due to the limited space available (8GB). Nevertheless I think the test served my purposes.
The JetStress tool is not very difficult to use. After you configure the test parameters it will run for a couple of hours and produce some performance logs which can be later analyzed. Figure 19 shows the Network occupation while JetStress was running. As you can see, only the dedicated gigabit NIC has relevant traffic.
Figure 19: NAS network performance during JetStress tests
The result was a pleasant surprise. All the performance indicators were within acceptable parameters, as shown in Figure 20. Notice the reduced write latency, only 3ms, which is better that some DAS I’ve seen.
Figure 20: Disk Subsystem performance indicators
I would like to share with you some lessons I learned during the whole process:
- Don’t forget to change the HOSTS file both on the NAS and the Exchange server. It’s very important that you do this, or you’ll end up using the LAN NIC and not the dedicated interface.
- The NAS device and the Exchange Server should be on the same AD forest. Don’t try putting the NAS server on a Workgroup.
For small and medium-size organizations that cannot afford the expense of Fibre Channel or IP-based SANs, NAS can offer flexible administration and management combined with easy deployment and maintenance.
To conclude, Exchange on NAS is a proved and approved configuration. Most of the main storage vendors have an offer within this area. The HP device I had the privilege to test behaved really well, so I must rate it positively and recommend that you give it a try if you’re considering deploying NAS with Exchange.
Exchange 2003 and Windows Storage Server
Managing Exchange Storage with the Windows Storage Server 2003 Feature Pack
Microsoft Exchange Server 2003, Windows Storage Server 2003, and HP Network Attached Storage (NAS)
HP StorageWorks Service Release Feature Pack Deployment Guide – Fourth Edition
Microsoft support policy on the use of network-attached storage devices with Exchange Server 2003
Exchange Server and network-attached storage
Using Exchange Server with Storage Attached Network and network-attached storage devices
Windows Catalog – HP ProLiant DL380 G3 iSCSI Storage Server