CS533 Concepts of Operating Systems

Class 18

File Systems

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Questions

Why does read-optimized block placement perform very poorly for a write-dominated workload?

How should free space be managed for a read-dominated workload?

How should free space be managed for a write-dominated workload?

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Questions

What impact will the current rapid increase in disk capacity and decrease in cost per Mbyte have?

o What if disk space was free?

With intelligent disk controllers should the file system manage placement at all?

What issues should concern a file system designer, beyond performance?

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Questions

How do mirroring and RAID-5 increase the reliability of file data?

o What kinds of failures can be tolerated?o Why might you choose mirroring over RAID-5?o Why might you choose RAID-5 over mirroring?

If a storage device migrates blocks dynamically between mirrored and RAID-5 storage, how can file system software keep track of where data is?

If the storage system is log-structured, does the file system above it need to be log-structured?

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Questions

Need file system software above HP AutoRAID concern itself with free-space management?

Would the system benefit from using a device interface at a higher level of abstraction?

o Why not implement the file abstraction at the device level?

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What next?

Final will be a take homeo Shouldn’t take more than a couple of hours