Storage Devices Flashcards
What is a Block Device?
A peripheral storage device, such as an HDD or SSD.
TRUE/FALSE: Hard Disk Drives are the last remaining mechanical component of modern computers.
TRUE.
Describe wear-leveling.
The spreading of writing operations across all memory cells to ensure no cell wears out immediately from overuse.
What is erasure coding?
A data-protection technique to ensure bits can be recovered even if one memory cell degrades. Often simply done through repeated memory fragments and storage.
What is bad-block tracking?
The process of keeping track of blocks that have gone bad (usually from overuse), so we can avoid them.
TRUE/FALSE: Optimal scheduling optimizes on throughput.
FALSE: Optimal scheduling is modular; It can be defined by the user to optimize for latency or fairness instead, for example.
TRUE/FALSE: Optimal scheduling uses Dynamic Programming to achieve efficient and complete scheduling.
FALSE: Optimal scheduling is NP-complete, since we don’t know what comes in, and to achieve a decent approximation, a Greedy approach is used.
What is I/O Q-Depth?
The Queue-Depth for currently waiting I/O operations.
TRUE/FALSE: Random writes can be made sequential using a log-structured strategy.
TRUE.
What is Direct I/O?
The movement of data directly from the source buffer to a memory device (we did this in project 4!).
What is Scatter/Gather I/O?
A single read/write request being able to collect data blocks from many disjoint locations.
TRUE/FALSE: We perform Read/Write amplification to improve our I/O efficiency.
FALSE: Read-write amplification is bad! We over-perform due to block nature of read/write.
What’s the major tradeoff with compression?
Performance for capacity.
What is sharding?
When a logical chunk of data is split into smaller chunks. Used for when a database contains too much data for a single machine to handle efficiently.
What is replication?
Data replication stored for recovery purposes.
