CCM export process as part of DB migration - badly defragments the disk. Any root cause known?
We are preparing for our upgrade from SQL Server to DB2 and from 6061 to 702. We are using the "repotools-xxx -exportConcurrent" and "repotools-xxx -importConcurrent" commands to transfer the data from the existing SQL Server databases to the new DB2 databases.
We have run thru the process a number of times in our QA/Staging environment. GC, JTS, RM, QM, and DCC all work perfectly. We have however run into an intermittent error with exporting our biggest database - i.e. CCM ( ~ 1 TB )
At 80% (about 7 hours into the CCM exportConcurrent command), the job raises an exception stating that a "File System Limitation" has occurred. We checked and before running the command, the disk drive was 0% fragmented. However, after the command failed, it is 83% fragmented. This has happened in the past and we sometimes succeeded in defragmenting completely or partially, but not always. After a few tries, the disk still remains badly defragmented.
2 answers
I would suggest to open a case with support. They can get the logs and details about the error message.
Comments
Thank you Ralph for your answer. We did open a case with support and awaiting a feedback.
It is necessary to work with support to find out what the root cause of the file system limitation error is. I am pretty sure that the fragmentation is of no concern. From my experience with disk fragmentation this should not cause anything. If you would use an SSD for the drive it would even not consider fragmentation a thing.
Thank you for sharing your experience and thought. It gave me another perspective.
On SSDs, fragmentation is largely irrelevant. On hard disks backed up by SSD caches (such as Optane) or large memory caches, the effects of fragmentation are usually mild.
Fragmentation is just a fact of life. Almost anything you do that creates large files that span free block sizes will cause fragmentation. On hard disks without large SSD/memory caches, defragmenting the disk should be regular housekeeping. Once a month seems like the least often you should do this.
Do you use the external storage option for the SCM data?
Might be using this option would make things easier.
After the db migration you can use the external storage or you can revert the changes.
greetings georg.