the write thread and path to store files on Vault Store

Hello,I'd like to know , when store files on the VaultStorePartitionfor one archive task ,like archive one mailbox, It will be multi thread write or single thread?

Is it can be configed?

Or only when archve multi-mailbox at the same time ,then the write thread will be multithread.

Bytheway, another question.

is there any way to identiy the files stored on the VaultStorePartition belong to different task(like different mailbox) through the file's store directory or name? 

Thank you for your help