kern/143126: [ata] Data loss on read timeout

[Andrey Russev]

>Number:         143126
>Category:       kern
>Synopsis:       [ata] Data loss on read timeout
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Jan 23 14:50:01 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Andrey Russev
>Release:        8.0
>Organization:
>Environment:
FreeBSD mizar 8.0-RELEASE FreeBSD 8.0-RELEASE #1: Sun Nov 29 02:44:55 EET 2009     root at mizar:/usr/src/sys/i386/compile/MIZAR  i386
>Description:
Sometimes (possibly on heavy loads of disk) kernel prints messages like:
ad6: TIMEOUT - READ_DMA48 retrying (1 retry left) LBA=615699968
These messages appear while copy/move of large file in progress. Such timeouts do not interrupt commands and they finish _without_ errors.
In case mentioned above I figured out that data from previous 64k block (LBA=615699968-128) was damaged (first ~30% bytes are correct). Second copy command (after unmount/mount) makes exact copy of data.

>How-To-Repeat:
I don't know. It occurs at random intervals.
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: