File Cache as Secondary Cache

[MrCroxx]

To balance the large total data volume, the low capacity of memory and the high latency of S3, RunKV can use the remaining space of the disk as secondary cache, or File Cache.

There are some considerations about File Cache:

• Moderate the unbalance of memory IOPS and disk IOPS.
• Should not introduce much latency to the read/write critical path.
• Avoid page cache usage.
• Avoid push much pressure down to the file system.

Ref: #44 .

[MrCroxx]

Refer to: singularity-data/risingwave#3556.