Hi, sabujp wrote on 2008-08-04 23:18:41 -0400 [[BackupPC-users] clustered file system and multiple servers]: > > Can a dev let me know if the files in the pool are FLOCK'd before writing,
use the force, read the source. "grep -r flock backuppc-3.1.0" suggests that flock is used, but not on pool files. Not surprising, considering BackupPC_link and BackupPC_nightly (or two instances of BackupPC_link) may not run concurrently (BackupPC_link is responsible for entering new files into the pool). Come to think of it, the reason for this restriction is of a different nature: BackupPC_nightly sometimes needs to rename pool files (with a common BackupPC hash, when one or more files out of the chain are deleted), while BackupPC_link may insert a new file with the same BackupPC hash. You can't prevent the resulting race condition with flock() - at least you don't effectively change anything in the single-threaded case (you'd need a rather global lock). > i.e. is there a chance that two servers backing up into the same top level > data directory could "mangle" a file in the pool in this manner? I don't think you'd have mixed file contents (or, effectively, a corrupt compressed file), but there seems to be a chance of linking a file in a backup to the wrong pool file (wrong contents altogether). You could probably use flock() to prevent two instances of BackupPC_link/BackupPC_nightly running simultaneously on different servers, but there are more things you would want to think about (running BackupPC_nightly on more than one server does not make much sense, even if they don't run concurrently; limiting simultaneous backups over all servers; ensuring BackupPC_dump is not run twice simultaneously for the same host ...). In short: sharing a pool between servers is currently not supported. Regards, Holger ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/
