why does juicefs have multiple storage layer?

[frankxieke]

The storage format of one file in JuiceFS consists of three levels.

I am wondering why juicefs design these three levels? Could you give me a hint?

[frankxieke]

• looking forward your reply

[xiaogaozi]

The short answer is: "chunk" is for speed-up seek big file, "slice" is for random write file, "block" is for speed-up read from and write to object storage.

[frankxieke]

thanks for your answer.

but i am still wondering why "slice is variable size , and this is for rand write file?'

does it have any more details i can learn?

[davies]

A pwrite() can happen on anywhere on a file, and has any number of bytes, so a slice is used represent one or multiple continuous writes.