A computer-implemented method of managing metadata storage for placeholders of files in a storage virtualization system: storing, on a secondary storage of a computing device, a placeholder for a file, wherein data of the file is stored remotely from the secondary storage, wherein the placeholder comprises a sparse data stream containing none or some but not all of the data of the file and information which enables the remotely stored data of the file to be retrieved; receiving a request to store metadata (302, 310) associated with the file; and storing the metadata as a Binary Large Object, BLOB, in a secondary data stream of the placeholder, wherein the secondary data stream comprises a plurality of BLOBs, each containing different types of metadata associated with the file, including at least a storage virtualization provider supplemental properties BLOB and a file format properties BLOB, i. the storage virtualization provider supplemental properties BLOB comprises properties that describe the file in the context of a storage virtualization provider that is configured to retrieve the remotely stored data of the file as needed, such as whether the file is checked out, who last modified the file, and whether the file is shared between two or more users, and ii. the file format properties BLOB contains information that is derivable from the contents of the file itself, assigning, based on the type of metadata contained in the newly stored BLOB, a BLOB identifier with a flag to the newly stored BLOB, wherein the flag indicates that, in response to the placeholder being converted to a regular file, - the BLOB is to be deleted from the secondary data stream in case it has been stored as a file format properties BLOB, and - the BLOB is to be retained in case it has been stored as a storage virtualization provider supplemental properties BLOB; fetching the remotely stored data of the file and writing it to the secondary storage, thereby converting the placeholder to a regular file; and determining, for each of the plurality of BLOBs, based on a flag associated with a respective BLOB of the plurality of BLOBs, to delete the BLOB from the secondary data stream in response to the placeholder being converted to a regular file. storing, on a secondary storage of a computing device, a placeholder for a file, wherein data of the file is stored remotely from the secondary storage, wherein the placeholder comprises a sparse data stream containing none or some but not all of the data of the file and information which enables the remotely stored data of the file to be retrieved; receiving a request to store metadata (302, 310) associated with the file; and storing the metadata as a Binary Large Object, BLOB, in a secondary data stream of the placeholder, wherein the secondary data stream comprises a plurality of BLOBs, each containing different types of metadata associated with the file, including at least a storage virtualization provider supplemental properties BLOB and a file format properties BLOB, i. the storage virtualization provider supplemental properties BLOB comprises properties that describe the file in the context of a storage virtualization provider that is configured to retrieve the remotely stored data of the file as needed, such as whether the file is checked out, who last modified the file, and whether the file is shared between two or more users, and ii. the file format properties BLOB contains information that is derivable from the contents of the file itself, i. the storage virtualization provider supplemental properties BLOB comprises properties that describe the file in the context of a storage virtualization provider that is configured to retrieve the remotely stored data of the file as needed, such as whether the file is checked out, who last modified the file, and whether the file is shared between two or more users, and ii. the file format properties BLOB contains information that is derivable from the contents of the file itself, assigning, based on the type of metadata contained in the newly stored BLOB, a BLOB identifier with a flag to the newly stored BLOB, wherein the flag indicates that, in response to the placeholder being converted to a regular file, - the BLOB is to be deleted from the secondary data stream in case it has been stored as a file format properties BLOB, and - the BLOB is to be retained in case it has been stored as a storage virtualization provider supplemental properties BLOB; - the BLOB is to be deleted from the secondary data stream in case it has been stored as a file format properties BLOB, and - the BLOB is to be retained in case it has been stored as a storage virtualization provider supplemental properties BLOB; fetching the remotely stored data of the file and writing it to the secondary storage, thereby converting the placeholder to a regular file; and determining, for each of the plurality of BLOBs, based on a flag associated with a respective BLOB of the plurality of BLOBs, to delete the BLOB from the secondary data stream in response to the placeholder being converted to a regular file.