Support for worm cartridges realized by linear tape file system (LTFS)

Abstract

When a WORM cartridge is formatted for Tape File System (LTFS) in advance, such as prior to shipment, Linear Tape File System Library Edition (LTFS LE) is expanded by software to reduce consumption of the index partition and to support elimination of the appending of unnecessary data. More specifically, instead of recording metadata in the index partition during normal unmounting, the metadata is recorded in separate local storage such as on hard disk drive (HDD), and the index partition is updated only when the cartridge is ejected from the library. In this way, the present invention is able to significantly reduce the frequency of index partition updates. Because an update occurs only when the user intentionally ejects a cartridge, overflow of the index partition before overflow of the data partition can be prevented.

Claims

1. A file system for eliminating the appending of unnecessary data created when a built-in tape in a tape cartridge mounted in a tape drive being used is accessed, to reduce consumption of capacity in a Write Once Read Many (WORM) index partition, the tape cartridge containing a built-in tape divided into two WORM partitions, the history of a plurality of files and metadata including the allocation of one or more recorded files being recorded in one WORM data partition, and metadata being recorded in the WORM index partition, wherein the file system, in response to an access request for a file on a tape cartridge mounted in a tape drive, enables: metadata recorded in the WORM index partition to be read; the read metadata to be written to an index area in local storage; metadata written to the index area to be used without using the metadata recorded in the WORM index partition in response to an access request to a file; determination of whether the access request for metadata written in the index area is accompanied by an update of the metadata; and writing the metadata written to the index area to the WORM index partition when it has been determined that the access request is accompanied by an update of the metadata.

2. An LTFS LE (Linear Tape File System Library Edition) file system including the file system according to claim 1, wherein the file system is a LTFS (Linear Tape File System), the tape cartridge mounted in the tape drive is a preformatted WORM cartridge, and the LTFS LE file system responds to access requests for the tape cartridge inserted into a tape library via an interface.

Description

BRIEF EXPLANATION OF THE DRAWINGS

(1) FIG. 1 is a diagram showing an example of information recorded on a tape cartridge.

(2) FIG. 2 is a diagram showing a view of directories in LTFS LE as an example in which tape libraries including inserted tape cartridges AAA000, BBB000 and CCC000 have been mounted using LTFS LE.

(3) FIG. 3 is a diagram showing the unmounting and mounting flow when reading and writing occur.

(4) FIG. 4 is a diagram showing an example of a table T of the present invention.

(5) FIG. 5 is a diagram showing the flow when access occurs in the present invention.

(6) FIG. 6 is a diagram showing the flow when a tape cartridge is ejected in the present invention.

EMBODIMENT OF THE INVENTION

(7) The present invention assumes that a WORM cartridge formatted for LTFS in advance, such as prior to shipment, is being used.

(8) The preparation of WORM cartridges formatted for LTFS in advance, such as prior to shipment, is not currently in practice, but is not technically difficult to realize.

(9) In the present invention, an area is prepared in local storage operated by the LTFS LE, such as the HDD of a PC, for storing the metadata of each cartridge and file data to be written to an index partition.

(10) This area is referred to as the index area.

(11) An index area may be prepared only for each cartridge managed by the LTFS LE.

(12) A table T indicating the access status of each cartridge by the LTFS LE is also prepared.

(13) FIG. 4 is a diagram showing an example of a table T of the present invention.

(14) There are three different access statuses as shown below, and 1, 2 or 3 is recorded in the table T for reference purposes.

(15) 1: The cartridge has not been accessed.

(16) 2: The cartridge has been accessed, and the index area was not updated after index partition information was copied to the index area.

(17) 3: The cartridge has been accessed, and the index area was updated after index partition information was copied to the index area.

(18) The table T may be stored in the memory used by the LTFS LE or may be stored in local non-volatile storage such as on an HDD which can be reused when the LTFS LE process has been ended and is restarted.

(19) Three different statuses (1, 2, 3) can be used in the table T to indicate whether or not a cartridge has been accessed and whether or not the index area has been updated. This is the specifying feature of the present invention.

(20) When the user accesses a file and a cartridge inside a tape library is unmounted from the tape drive, a tape cartridge has to be accessed.

(21) In a conventional LTFS LE, the index partition of a tape cartridge is accessed when the tape cartridge is accessed.

(22) In the present invention, the index area is accessed or not accessed depending on the situation.

(23) FIG. 5 is a diagram showing the flow when access occurs in the present invention.

(24) More specifically, as shown in FIG. 5, the table T is referenced, the index partition information is copied to the index area during initial access to the cartridge, and the index area is then accessed.

(25) In Step 100, the process is initiated to respond to an access request for a file on a tape cartridge mounted in a tape drive.

(26) In Step 110, the table T is referenced to acquire the access status of the tape cartridge.

(27) In Step 120, it is determined whether or not the access status has been set to 1.

(28) If the access status has been set to 1, the tape cartridge is mounted in a tape drive, and metadata recorded in the WORM index partition is read from the mounted tape cartridge in Step 130.

(29) In Step 140, the read metadata is written to the index area of local storage.

(30) In Step 150, the access status is set to 2 in the table T.

(31) In Step 160, the metadata written to the index area is used to respond to the access request for the file (the metadata recorded in the WORM index partition is not used).

(32) In Step 170, it is determined whether or not an access request for the metadata written to the index area is accompanied by a metadata update.

(33) If the access request is accompanied by a metadata update, and the access status in the table T is not 3, the access status is updated to 3 in Step 180.

(34) In Step 190, the response to the access request is completed.

(35) By using a table T in this way to access a tape cartridge, the index area can be accessed after the cartridge has been mounted instead of continuing to access the index partition as in a conventional LTFS LE.

(36) FIG. 6 is a diagram showing the flow when a tape cartridge is ejected in the present invention.

(37) When a tape cartridge is ejected from the LTFS LE, as shown in FIG. 6, the information in the index area is written to the index partition if necessary before the tape cartridge is ejected.

(38) In Step 200, the tape cartridge ejection process is initiated.

(39) In Step 210, the table T is referenced to acquire the access status of the tape cartridge.

(40) In Step 220, it is determined whether the access status has been set to 3.

(41) If the access status has been set to 3, the metadata written to the index area is written to the WORM index partition in Step 230.

(42) If this status has been set, the metadata written to the index area of the local storage is no longer needed and may be deleted.

(43) This operation may be timed to coincide with the cartridge unmounting process when the cartridge is ejected.

(44) In Step 240, the information related to the access status of the tape cartridge is deleted from the table T.

(45) In Step 250, the tape cartridge ejection process may be performed in the same manner as a conventional LTFS LE.

(46) In Step 260, the tape cartridge ejection process is completed.

(47) As explained in FIG. 5 and FIG. 6, the table is set to T (=1) when the table T has not been set to either T (=2) or T (=3).

(48) From FIG. 5 to FIG. 6, the updating, referencing and use of settings in the table T follow the sequential order T (=1), T (=2), T (=3).

(49) Viewed another way, three different statuses (1, 2, 3) are set in the table T in the flow from FIG. 5 to FIG. 6, and whether or not a tape cartridge has been accessed can be identified by groupings 1, 2 and 3, and whether or not the index area of a tape cartridge has been updated can be identified by groupings 2 and 3.

(50) Because the information in the index partition is updated only when a cartridge is ejected from the LTFS LE, the frequency at which the index partition is updated can be significantly reduced.

(51) A cartridge is ejected from the LTFS LE only when the user expressly operates the LTFS LE. Therefore, the index partition is updated only when the user expressly does so.

(52) As a result, the index partition can be prevented from overflowing before the data partition does so.

(53) When a cartridge is inadvertently discharged from the tape library without being expressly ejected, the most recent information may not have been written to the index partition.

(54) However, no data is lost because the latest index information has been written to the data partition. The latest index information can then be recovered through the usual LTFS recovery process.

(55) The present invention may be embodied by a person skilled in the art using technical concepts in other categories. For example, a program could be created to execute in a computer each step in the method of the present invention.