How (1) prefetched data is stored (2) client-cache is used

[myc724]

We are trying to understand format/mount options for tuning our JuiceFS setup for some applications. Could you let us know if any of our statement is in-correct? Thanks!

By default, …

• “juicefs format” create a volume with 4MB block-size
• “juicefs mount” configure a mount point as …
  • cache-size 1MB
  • buffer-size 300MB
  • prefetch 1 block in parallel

Every read “prefetch 1 block”, so it brings in at least 4MB of data. Then, JuiceFS client

• store the “in-use” key-value pairs in the 1MB cache.
• store the "rest of" prefetched data in the 300MB read/write buffer.

[davies]

By default, …

“juicefs format” create a volume with 4MB block-size

Yes

“juicefs mount” configure a mount point as …
cache-size 1MB

The default cache-size is 1GB.

buffer-size 300MB
prefetch 1 block in parallel

Yes

Every read “prefetch 1 block”, so it brings in at least 4MB of data. Then, JuiceFS client
store the “in-use” key-value pairs in the 1MB cache.

1GB

store the "rest of" prefetched data in the 300MB read/write buffer.

cache-size is the total amount of data cached in disk (under /var/jfsCache/xxx/).
buffer-size is the amount of memory used for read/write.

[myc724]

My mistake. The default cache size is 1GB. Thanks!