Host, operating method of host and storage system

Abstract

A host includes: an index tree storing an index including information for identifying a versioning key; and an index update buffer storing a write key included in data subject to a write request and the versioning key corresponding to the write key. When a preset update condition is satisfied, the host transfers the versioning key stored in the index update buffer to the index tree, and when the index update buffer requires recovery, the host designates a recovery section of memory of the storage device including data corresponding to the versioning key which has not been updated to the index tree, to be read by a plurality of threads, reads data included in the recovery section from the storage device through the plurality of threads, and inserts the read data into the index update buffer to recover the index update buffer.