Infrequent EPOS errors after encrypting small 1.8" platter size Lenovo HDDs

Article:TECH151192  |  Created: 2006-06-26  |  Updated: 2007-01-31  |  Article URL
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Technical Solution


Infrequent EPOS errors after encrypting small 1.8" platter size Lenovo HDDs


Description Details:
EPOS errors are sometimes generated after encrypting small 1.8" platter size Hitachi's Lenovo Hard Disks.

GuardianEdge has received rare reports of EPOS errors after initial encryption when using the setting "recovery after power loss" combined with new generation small Lenovo drives with narrow tracks. These reports were researched by Lenovo and GuardianEdge, and a workaround as described below was tested and found to be a viable method to resolve the issue in those rare instances where it occurs.

GuardianEdge and Lenovo performed testing using new generation 1.8" Hitachi Lenovo drives with narrow tracks that are sometimes used in IBM X41 Tablet Notebooks. When using the "recovery after power loss" option within EP Hard Disk, the EPOS error was reproducible sometimes. In each test where the EPOS error was reproduced, the drive was easily recovered using the '"recover /a" utility within EP Hard Disk.

Lenovo's analysis indicated that the EPOS error was due to a single sector being written to repeatedly during initial encryption. This frequent write is most likely related to the data being written to the Encryption Plus File System to track sector-by-sector encryption as part of the design for "recovery after power loss". Lenovo hypothesized that with multiple writes to a sector on the new generation drive that has narrow tracks, damage to adjacent tracks may be occurring - a phenomenon called Adjacent Track Interference (ATI).

Further tests were done where the same drives were encrypted and decrypted repeatedly without using the "recovery after power loss" option. By changing this setting, the time to encrypt the same size hard drive took 20 minutes versus 36 hours with the previous setting. Even with dozens of encryptions and decryptions of the drives no EPOS errors were generated after the setting was changed. So, changing the initial encryption setting appears to be a viable workaround to prevent EPOS errors that seem to be related to Adjacent Track Interference (ATI) on small 1.8" hard drives with narrow tracks.

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