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Using Data Mirroring to prevent loss of redundancy following failed drive firmware download

IP.com Disclosure Number: IPCOM000031015D
Original Publication Date: 2004-Sep-07
Included in the Prior Art Database: 2004-Sep-07
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Abstract

When drives are shipped, they are running a certain level of firmware. As time progresses, defects in the shipping level of code may be uncovered, and updated versions made available. As a result, it is advantageous for the drive owners to download updated firmware as it becomes available, in order to protect themselves against the adverse effects of the defects. Unfortunately, downloading firmware to drives is risky and can lead to temporary or permanent loss of access to the device. In some cases, the risk associated with a download is greater than the risk associated with running an old level of code (or "downlevelled" code), so drive owners choose not to perform the code upgrade. This article describes a method that removes the risk of "loss of access" from the downloading procedure, thus allowing drive owners to keep their drives up to date without having to weigh up the associated risks.

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Using Data Mirroring to prevent loss of redundancy following failed drive firmware download

Many Storage System owners are reluctant to download new firmware to their drives, as there is a risk associated with this activity. The risk is that the download will cause the drive to fail. The impact of this failure depends on their drive configuration: If the drive is a JBOD (a single drive that is not part of a RAID array), then the failure of this drive will result in the loss of all data on it. If the drive is a member of a RAID array, then that array will become exposed or even degraded. Depending on the array configuration, the system may contain a single point of failure. Until the array is fully rebuilt, further disk failures could result in data loss.

Also, downloads can take ~45 seconds, during which time there is no direct access to the data on the drive.

This method involves identifying a drive to which firmware download is required and mirroring the data from this drive onto a HotSpare. The drive receiving the download will be referred to as the target drive.

A HotSpare is a drive that normally contains no customer data, but is contained in the system in order to replace an array member automatically should the member fail. In normal operation, if a HotSpare takes over from a failed member, the data is reconstructed from the remaining array members. The method described here requires you to mirror the data from the target drive to a HotSpare, almost like setting up a RAID 1 array.

HotSpares often exist in a "pool" of drives that are available to take over if necessary.

By mirroring all the data from an array member (or JBOD) onto a HotSpare, before downloading code, the system is fully protected against the loss of that target drive. The HotSpare can be swapped in instantly, reducing an array rebuild time to zero, hence removing the exposure previously described.

In the case of failure of...