An object store (ObS) or object storage device (OSD) enables the creation of self-managed, shared, and secure storage for storage networks. The device is accessed through a standard object interface. The standard OSD interface was defined in the Storage Networking Industry Association (SNIA) OSD working group. The protocol is embodied over a small computer system interface (SCSI) and defines a new set of SCSI commands, standardized as a T10 protocol.

The OSD Simulator is an implementation of an object-based storage device. It functions as a reference implementation compliant with the T10-OSD standard specification. The protocol is implemented over iSCSI (SCSI over IP). The simulator is a Linux user mode application and was tested with the open-source OSD initiator for Linux. This simulator uses the local file system to store objects: Partitions are translated to directories and user objects to files. The simulator uses GDBM (libgdbm, which is a GNU library) to store attributes.

IBM® OSD Simulator for Linux® is a simple implementation in the sense that it does not support concurrent execution of commands and it lacks performance guarantees. The team at IBM Haifa Research Lab developed a controller-like, scalable implementation of an object-based storage device called ObjectStone. The OSD Simulator is used as one of the tools for testing ObjectStone, providing a reference implementation of a T10-compliant target.

How does it work?

IBM OSD Simulator for Linux consists of three layers:

• An iSCSI target layer supporting SCSI requests with extended CDB as well as bi-directional data transfers.
• An SCSI-OSD layer implementing the T10-OSD protocol including CAPKEY security method.
• A simple device simulator that uses the local file system to store data and a local GDBM database to store objects' metadata.

This software contains the following features:

• Execution of OSD commands arriving from an iSCSI initiator in the T10-OSD protocol format. Commands may arrive from several initiators (each on its own iSCSI sessions) but are handled one at a time.
• Allowance of customer data and meta data transfer simultaneously on a single command.
• Allowance of data transfer up to 900 KB and metadata transfer up to 64 KB on a single command.
• Supported commands are as follows: CREATE,CREATE PARTITION,GET ATTRIBUTES,LIST, REMOVE, REMOVE PARTITION, READ, WRITE, CLEAR, FORMAT, SET_KEY, TEST UNIT READY, INQUIRY, REPOR_LUNS.
• Metadata transfer is done using the OSD attribute list format, enabling transfer of multiple attributes within a single command. Each transfered attribute can be up to 1000 bytes long.
• Support for all standard attributes' behavior except for collections attributes.
• Support for, at most, 10,000 partitions, each holding up to 10,000 objects at a time.
• The following OSD Security methods are supported: NOSEC, CAPKEY (excluding the SET MASTER KEY command).

Unsupported features:

• OSD collections.
• OSD commands that are not mentioned above.
• "CREATE" command supports creation of only one object in a single command.
• Running of several simulators from the same directory.
• Recovery from failure or shutdown.
• CMDRSP and ALLDATA security methods (as defined by the OSD standard).

The simulator handles commands in a FIFO manner.

For further information, please see the following PDF files:

• Object storage: The future building block for storage systems (a position paper)
• Object storage: The future building block for storage systems (a presentation)

Please also see the IBM Haifa Object Store project's Web site for further information and for an overview of the OSD technology.

This software was developed as part of the Object Store project in IBM Haifa Research Laboratory.

The OSD Simulator was primarily developed by Allon Shafrir. Mr. Shafrir has been with IBM's Storage Technologies department since 2004. He holds a B.Sc. in electric engineering from the Technion, Israel Institute of Technology. He is currently pursuing a master's degree from Tel-Aviv University.

The iSCSI target code was developed by Petra Reshef. Mrs. Reshef holds a B.Sc. in computer science from Haifa University and has been with IBM since 2000.

Other team members that contributed to this implementation include Ohad Rodeh and Liran Schour.