1. Disk Access

2. Seek Algorithms FCFS SSTF SCAN - ssd in preferred direction
CSCAN - outer to inner, ssd, jump to outer
FSCAN - scan for only those at start of scan
nSCAN - only first n requests
LOOK - lookahead & change direction
C-LOOK - outer to inner & jump

3. Rotation Algorithms SLTF – Shortest Latency Time First
latency, by sector position
SPTF - Shortest Positioning Time First
Time to position the access-head
SATF – Shortest Access Time First
close coupling of CPU and disk
processor knows rotational position of the disk at any time

4. Other considerations Cache Fragmentation Partitioning Compression
Record blocking
Hot-spot detection (speeds up access)

5. problems
Write-through
Coherency is high
Lazy-write
Low coherency

6. RAID 0 - striping - no Fault Tolerance 1 - mirroring (see my patent)
2 - bit-striping with Hamming parity stripes
3 - like 2 but XOR ECC stripes
4 - large block stripes + XOR ECC stripes
5 - like 4 but parity with data
striped disks + 2 mirrors
10 - mirrored disks + a striped pair