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If you're considering stepping up to SAN, the following tips can help you make informed decisions when selecting the hardware and technologies that you use.
1. Determine How You Plan to Use Your SAN Storage
Before you start building your SAN, decide exactly what you plan to use it for. Are you consolidating storage consolidation for multiple servers? Are you planning to use the storage for backup to disk? Or will you be doing both? It's easier to make the correct decision about your SAN storage if you have a clear picture of how you plan to use it.
2. Select the Correct Level of RAID
Aside from consolidating storage, a disk array can provide fault tolerance by using RAID (redundant array of independent disks) technology. RAID distributes data across the disks on the array, and uses mathematical algorithms to reconstruct data if one of the disks fails. Because RAID requires additional calculations and storage space, the following table helps you choose the RAID level that's right for you.
3. Size Your Needs Today and Plan for Growth
Determine the amount of storage your SAN requires. If you plan to use the SAN solely for consolidating server storage, add the current disk space being used on every server. Take the total and add 50% per year for growth plus extra drive space for RAID redundancy. If you are using the SAN for backup to disk, take the preceding total and multiply it by two.
4. Chose a Name You Can Trust
A SAN must be dependable. The performance of RAID disk arrays can vary widely from manufacturer to manufacturer. Select SAN storage hardware from a manufacturer with a proven track record. Review the testing guidelines for the products.
5. Increase Reliability by Using Redundant Paths to the Disk Array
With a SAN, your storage is now external to your servers. If you can't get to it, you're dead in the water. Look for an array that has two Fibre Channel or GigE iSCSI ports. If one path fails your servers can automatically connect via the other path.
6. Use Dual Processors to Increase Throughput
Dual processors increase a disk array's speed by providing two processors to handle incoming requests. Requests from the servers are automatically load balanced between two service processors in the disk array. Each processor has its own cache, so the array can handle tasks in parallel, which provides a noticeable improvement in speed.
7. Go with Fibre Channel Connectivity for Ultimate Performance
If your SAN requires high levels of performance, select use Fibre Channel connectivity, which uses special Fibre Channel host bus adapters (HBAs) and optical fiber. Fibre Channel switches and cables are more expensive and require more expertise to install and manage, but Fibre Channel is a better choice for environments that demand a consistently high level of performance.
8. Choose iSCSI Connectivity for a Cost-Effective Solution
If high performance levels are not your top consideration, iSCSI is a natural choice for most SMBs. It keeps costs down by using commodity cables with standard GigE ports and switches, which are also easier to set up and configure for most IT departments. iSCSI can be used with all but the most demanding applications.
9. Look for Hot Swappable Components
For speed and convenience, select a SAN disk array with hot-swappable components. Components such as disk drives, power supply, cooling fans, or controllers should be customer-replaceable in case they ever need to be changed. Having the ability to easily swap in higher capacity disks makes it practical to start small and add storage capacity as your needs grow. It's also a good idea to have a spare kit on hand.
10. Make Sure Your Hot Spare Can Be Mapped Automatically to Replace a Failed Drive
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