On Mon, Jul 4, 2016 at 2:52 PM, 'Steffen Heil (Mailinglisten)' li...@steffen-heil.de [firebird-support] <firebird-support@yahoogroups.com> wrote:
Late, but I was away... > > I have a database on a hard drive which is failing. The hard drive already > has some bad sectors and we are about to replace it. > > Now I have a backup of that database created with gbak that I could use. > However I am not sure if the hard drive was still fine, when the backup was > created. > If the backup succeeded, then the database file had no corrupted data pages or system pages. It might have corrupted pages in indexes on user tables. > On the other hand, I can right now access the database just fine and I > could try to simply copy it. Copying it is a good option if a backup fails - you'll have something to try to recover from. As third option I could create a new backup to external media right now. > That would have been the best option. If the backup succeeded, then you would know that all your data is fine and up to date. > > Now my questions: > - Is there any way to check a copied database file for corruption? If the file copy works without error (no file system I/O error) can I be > sure or is there a command to be sure, if the file is completely intact? > Gfix -v works on the physical level. Backup or sweep checks the logical consistency of data and system structures but not user indexes. > - If I restore the backup and gbak does not report an error, can I be sure > that everything is okay? > Yes. If there were bad index pages, they will be replaced. > - If I create a new backup and gbak does not report an error, can I be > sure that the new backup is okay? > Yes, the backup will be OK - yes there have been bugs in backup but they were generally mishandled dependencies ... not bad pages > > There used to be a checksum in the page header, but IIRC that field was > abandoned. > Decades ago. Good luck, Ann
