You are viewing a plain text version of this content. The canonical link for it is here.
Posted to derby-dev@db.apache.org by "Suresh Thalamati (JIRA)" <de...@db.apache.org> on 2004/12/13 19:42:59 UTC
[jira] Assigned: (DERBY-96) partial log record writes that occur because of out-of order writes need to be handled by recovery.
[ http://nagoya.apache.org/jira/browse/DERBY-96?page=history ]
Suresh Thalamati reassigned DERBY-96:
-------------------------------------
Assign To: Suresh Thalamati
> partial log record writes that occur because of out-of order writes need to be handled by recovery.
> ---------------------------------------------------------------------------------------------------
>
> Key: DERBY-96
> URL: http://nagoya.apache.org/jira/browse/DERBY-96
> Project: Derby
> Type: New Feature
> Components: Store
> Versions: 10.0.2.1
> Reporter: Suresh Thalamati
> Assignee: Suresh Thalamati
>
> Incomplete log record write that occurs because of
> an out of order partial writes gets recognized as complete during
> recovery if the first sector and last sector happens to get written.
> Current system recognizes incompletely written log records by checking
> the length of the record that is stored in the beginning and end.
> Format the log records are written to disk is:
> +----------+-------------+------------------+
> | length | LOG RECORD | length |
> +----------+-------------+------------------+
> This mechanism works fine if sectors are written in sequential manner or
> log record size is less than 2 sectors. I believe on SCSI types disks
> order is not necessarily sequential, SCSI disk drives may sometimes do a
> reordering of the sectors to optimize the performance. If a log record
> that spans multiple disk sectors is being written to SCISI type of
> devices, it is possible that first and last sector written before the
> crash; If this occurs recovery system will incorrectly interpret the
> log records was completely written and replay the record. This could
> lead to recovery errors or data corruption.
> -
> This problem also will not occur if a disk drive has write cache with a
> battery backup which will make sure I/O request will complete.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://nagoya.apache.org/jira/secure/Administrators.jspa
-
If you want more information on JIRA, or have a bug to report see:
http://www.atlassian.com/software/jira