Cloud Storage Gateway (CSG) file gateways support the following storage classes of OSS buckets: Standard, Infrequent Access (IA), and Archive.
If the archive feature is not enabled for a file gateway, a read operation on an archived file on the gateway also triggers a request to restore the file. For more information about how to configure the archive feature, see Step 6 in the "Manage shares" topic. If the file gateway uses a Network File System (NFS) share, no error is returned, but a certain level of I/O latency occurs. If the file gateway uses a Server Message Block (SMB) share, a short-lived error occurs, and the read operation is successful after the restoration process is completed.
When a client writes a file to a file gateway, the gateway records at least two actions: writing the file and setting the file modification time. The gateway merges the two actions where possible. However, the gateway may still send multiple operations on the object to the bucket where the object is stored. The CopyObject operation is called to store the file modification time as a piece of metadata of the object in the bucket. If the object is an Archive or Cold Archive object, this operation requires object restoration, which takes some time to complete. This increases the time required for object uploads and even causes upload failures if not enough time is left to upload data in the cache. We recommend that you do not connect a gateway to an Archive bucket or a Cold Archive bucket. If files that are written from a file gateway to OSS are infrequently modified, we recommend that you store the files as objects in a Standard bucket or an IA bucket first and configure a lifecycle rule that changes the storage class of the objects to Archive or Cold Archive. This reduces unnecessary restoration operations and optimizes storage costs and efficiency.