Storage system

Details Storage system Storage system

1997-07-07

2001-07-17

Lee, Thomas (Department: 2182)

Error detection/correction and fault detection/recovery

Data processing system error or fault handling

Reliability and availability

C714S030000, C714S046000

Reexamination Certificate

active

06263454

ABSTRACT:

TECHNICAL FIELD
The present invention relates to devices for storing computer data and relates particularly to diagnostics and status monitoring.
BACKGROUND ART
It is known to provide status monitoring in a disc drive and U.S. Pat. No. 5,450,609 describes one such system in which an array of disc drives includes a facility for status monitoring and for warning the user of a problem. The warning facility described is not very different in scope from the known facility on existing tape drives of a warning light indicating failure of a backup operation.
DISCLOSURE OF INVENTION
The present invention aims to provide a status monitoring and diagnostic facility for a storage device which takes account of the fact that the storage medium is removable and which diagnoses a wider set of error conditions than simply flagging imminent failure and which also takes account of the number of occurrences of a particular type of error.
According to the present invention we provide a system for storing computer data comprising:
a storage device having means for reading data from and writing data to removable media;
and a controller,
wherein the storage device comprises:
means to perform error diagnosis and to translate low-level error indicators into a plurality of high level error conditions;
means to communicate occurrence of these high level error conditions to the controller to trigger the provision of error messages to the user;
means for communicating different high level error conditions according to how many times a specified low-level error has occurred.
Thus, in systems implementing the present invention, the particular high level error conditions communicated depend on how many times a relevant low-level error has occurred. This feature enables the provision of a succession of different error messages to the user recommending different actions if an error persists.
The term ‘low-level error indicator’ is intended to cover both error codes and other relevant triggers generated in the storage device. Low-level error codes cover items such as unrecoverable read and/or write errors but there are also other relevant triggers for high level error conditions such as the rate at which data is being written, data relevant to the media being used etc. Low-level error indicators are normally generated by the firmware in the storage device.
The system may be configured so that only one high level error condition is communicated as a result of the occurrence of a low-level error indicator. However, very often more than one high level error condition may be triggered by the occurrence of a low-level error so that the user may receive a corresponding combination of error messages. In the embodiments to be described, the system comprises means for communicating different combinations of high level error conditions according to how many times a particular low-level error has occurred.
Preferably, the low-level error indicators are grouped into functional types and a predetermined sequence of high level error conditions is communicated according to how many times a low-level error of the same functional type has occurred.
Thus, in the embodiments to be described, the low-level errors are grouped into broad categories. If successive errors within one of these groups occur, this triggers different combinations of the high level error conditions.
In the embodiments to be described, the system comprises means for communicating different high level error conditions according to the elapsed time since the storage device was last cleaned. Many error conditions can be alleviated by running a cleaning cycle and so, in practice, this is often the first suggested error recovery step.
Preferably, the error messages are categorised according to severity. In the embodiments to be described there are three categories of severity: Information, Warning and Critical.
The system may comprise means automatically to initiate a predetermined sequence of error recovery steps according to the high level error conditions identified. This feature means that some error recovery or error prevention steps may automatically be initiated by the controller rather than the user. One possibility in the case of an autoloader (a system with a mechanism for automatically loading media into a storage device), would be an automatic cleaning cycle using specialised cleaning media.
Preferably, error status information is stored in the storage device in a standardised format. This feature enables backup software applications to interface with storage devices from different manufacturers which implement the present invention. In this way, the invention provides a technique whereby the way in which errors are detected and categorised for a particular storage device is device-specific and can be decided by the device manufacturer but within the context of a standardised scheme which enables all devices complying with the standardised format to interface with backup application software from different software providers in order to provide the user with consistent error indications.
There are different ways in which the controller may receive error information from the storage device. In one embodiment to be described, the system is configured so that the occurrence of high level error conditions is communicated to the controller at predetermined points in a storage operation. In another embodiment to be described, the system is configured so that the occurrence of high level error conditions is communicated to the controller whenever a new error is indicated by the storage device.
In the embodiments to be described, the storage device is a tape drive, but the invention applies also to other storage devices with removable media eg. optical disc drives.
The controller may be backup controller software running on a host computer. Alternatively the system may be part of network in which the controller is backup software running on a backup server on the network. However, the invention is not limited to these alternatives and the controller may be implemented in software and/or hardware and may be in a general purpose computer or a dedicated device, whether standalone or connected to a network. The system may comprise a plurality of storage devices such as in an autoloader or a coordinated array of storage devices.
Other aspects and features of the present invention will become apparent from the following description, claims and drawings.


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IBM TDB, vol. 37, No. 02B, Feb. 1994, p 241, “Keeping Users Aware of the Status of an Object Affected by Multiple Program”.
IBM TDB, vol. 37, No. 06B, Jun. 1994, pp 499-501, Operating Intervention Message Management for Tape Drive Displays.
European Search Report; EP 96305388.

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