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High-speed optical WANs are becoming indispensable for critical storage applications. Business continuance, remote mirroring and replication, and connecting regional data centers are all tasks that require optical WANs. With many optical options and prices, picking the best technologies and techniques to transport data is challenging.
Most storage apps are time-sensitive and require high throughput (bandwidth) and low latency with zero data loss. Effective bandwidth is a measure of how much of the available bandwidth can actually be used, taking into consideration dropped packets and retransmission due to congestion and protocol inefficiency. Some vendors, including Ciena Corp., Linthicum, MD, refer to effective bandwidth as "good put" vs. simply looking at a theoretical line speed number.
To pick a data transport to fit your needs, first consider your storage requirements:
- Distance. How far away do you need to keep a copy of your data?
- Bandwidth. How much data must be moved and in what timeframe?
- Cost. What's your budget?
- Recovery point objective. Can you afford data loss? At what point do you need to recover data from?
- Recovery time objective. How quickly do you need to recover?
- Latency. What are your applications' response time requirements?
When evaluating storage-over-distance network technology, keep the following items in mind:
- Throughput. How much bandwidth is available and how much is needed?
- Latency. What's the time delay and how does it impact the storage application?
- Packet loss. How much bandwidth is lost due to data retransmission?
- Variable bandwidth. What's the granularity of available bandwidth?
- Manageability. What are the networks' management capabilities, including diagnostics?
- Flexibility. Is the network service adaptable to changes in your storage environment and its locations?
- Resiliency. Are there diverse network paths, and does the network contain self-healing, rapid failover features?
- Budget. What are the initial upfront and recurring costs?
This was first published in August 2005