For the restore operations that use a key management server (KMS), the software gets the encryption key from the KMS for every restore operation. To improve the performance of restore operations, you can enable the CacheMasterKeyForRestores additional setting to cache the encryption key information of the storage pool or the storage policy copy for 24 hours.
For the restore operations that use the same storage pool or storage policy copy, the software uses the cached encryption key for the next 24 hours.