Mirror Raid and Hard Disk Failures
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Mirror Raid Is not always effective

We had "auto-rebuild" enabled on a mirror raid. This was a mistake as both drives developed faults at about the same time.

Drive "1" this drive decided that it wouldn't always start when the PC was booted. But it did start later on, presumably still with the data intact. But the controller would detect it as needing rebuilding and copy Drive "2" to it, without intervention.

Unfortunately Drive "2" also developed a fault, a few bad sectors. Consequently the bad sectors got "copied" to Drive "1". Not what was required.

Moral - Manual rebuilds only, investigate all errros!

Higher Failure rate of newer High Capacity Drives

The two drives in the mirror raid were getting a bit long in the tooth, so they can't be blamed for failing. But we've also recently seen early failure (multiple bad sectoring) of 160GB (internal, only a few months old) and 250GB (external, older but hardly used) drives (both Maxtors). In both cases the failure occured when the amount of disk space in use was being increased (ie an area of disk not previously used was being written / read). Unfortunately the external drive was being used as a backup for the internal drive, and it failed during the restoration. A messy consolidation of good data from both drives followed.

Moral - Don't rely solely on single external backups, they can fail.

"Inaccessible Boot Device" blue screen - Large (>120GB) Hard Drives, 48LBA and Acronis TrueImage 8

A hard disk bigger than the 120GB limit if 48LBA is not active was installed and Acronis True Image 8 used to copy and expand an old drive partition to it. True Image 8 did not check for 48LBA support in the BIOS, let alone the registry key activation in Windows, but still did the copy. Subsequntly the copy would not boot, but came up with the "Inaccessible Boot Device" blue screen. A good job the option to delete the data after copying hadn't been selected! A new BIOS (with 48bit LBA), a registry key update to Win2K and a new copy fixed it.

A utility such as a partition copier by a "big name" company should do all it can to guarantee that a copy will work, there must be a lot of people who have pre 48LBA BIOSes who are upgrading hard disks.  Acronis say they will address this.


2006 Camel Services Ltd. www.camel.co.uk