hashinaflashhashtablesforsolidstatedevices

hashinaflashhashtablesforsolidstatedevices内容摘要：

ash table excess 11/30/2020 10 Can we improve MB?  Reduces number of write operations to flash device  Batch Updates only when memory buffer is full  Updates are semirandom  (Key,Value) changes are maintained in memory  Query times are reasonable  Memory buffer search is fast  Relatively fast SSD random access and linear probing (See Paper)  Prefetch pages  MB has disadvantages  Sequential Page Level operations are preferred Fewer block updates  Limited by the amount of available memory Think large disk datasets. Updates may be numerous 11/30/2020 11 Introduce an On Disk Buffer  Batch updates from memory to disk are page level  Reduce expensive block level writes (time and cleans)  Increase Sequential writes  Increase buffering capability  Reduce expensive non semirandom Block Updates  May decrease cleans  Search space increases during queries  Incurred only if inserting and reading concurrently  However, less erasure time will decrease latency 11/30/2020 12 On Disk Buffering  Change Segment (CS)  Sequential Log Structure  sequential writes  stage() operation  Flushes memory to CS  Fast Page Level Operations  merge() operation  Invoked when CS is full  Combines CS with Data Segment  Less frequent than stage()  What is the structure of the CS? 11/30/2020 13 Change Segment Structure v1 14 Buckets are assigned specific Change Segment Buckets. Change Segment Buckets are shared by multiple RAM buffer buckets. Memory Disk Bounded Buffer (MDB)  Associate a CS block to k data blocks  Semi random writes  Only merge() full CS blocks  Frequently updated blocks may incur numerous (k1) merge() operations  Query times incur an additional block read  Packed with unwanted data 11/30/2020 15 Change Segment Structure v2。