## Accessibility and Data Movement

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**Where data lives affects how you can use it**

- **Network bandwidth**: Moving terabytes takes time
- **Physical proximity**: Data locality matters (latency, throughput)
- **Access patterns**: Random vs sequential differs drastically

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Data accessibility depends on both network infrastructure and physical proximity.
Transferring large datasets across networks faces bandwidth constraints that can make certain workflows impractical.

A multi-terabyte dataset that takes days to transfer may make remote processing infeasible.
Physical storage architecture affects performance significantly.

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:::{admonition} Key Terms
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**Latency**: Time delay to access data  
**Throughput**: Volume of data transferred per unit time
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:::{admonition} The Data Movement Problem
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Sometimes it's faster (and more practical) to ship a hard drive than transfer over the network
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Data stored on local SSDs provides dramatically different access patterns compared to network-attached storage.
Random access patterns can be hundreds of times slower on spinning disks compared to sequential reads.

These realities mean that where data resides relative to computation becomes a critical design decision.
Sometimes the optimal strategy is to move computation to the data rather than data to the computation.

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