On Fri, Apr 11, 2014 at 6:55 AM, Grzegorz Sikorski <g.sikor...@kelvatek.com>wrote:
> Hi Richard, > > We do fsck on the startup. Occasionally, there are some errors, so we > decided to do 'fsck -p' to fix them before mounting the filesystem. Here is > how we then mount the actual filesystem: > /dev/mmcblk0p2 on /media/DATA type ext4 (rw,relatime,barrier=1, > journal_checksum,nodelalloc,data=journal,usrquota) > > I am not an expert in ext4, so I am not sure it is the best way to mount, > but as far as I read on some forums, this is the safest (and slowest!) > option. > If EXT4 is also corrupting, that is evidence to support my theory that the SD card is not synching correctly and is performing writes out of order. And if that is the case, then there is nothing you can do to prevent corruption on power-loss, to SQLite or any other database. All you can do is try to minimize your exposure. (1) Using WAL mode is good. But the usage pattern makes a difference too. Please make sure you have at least one process that opens the database (in WAL mode) and keeps it open all the time. That processes doesn't have to do anything with the database other than hold it open. SQLite deletes the WAL file when the last connection closes. By having one process hold the database open, that prevents the WAL file from being deleted, which reduces the risk of corruption. (2) Make sure you are not checkpointing too frequently. Remember that the power-loss corruption vulnerability only occurs during checkpoint. You have to checkpoint *sometime*. Just try to make sure it isn't too often, so that the risk of taking a power loss during a checkpoint is reduced. (3) Make periodic backups of the database file using the SQLite backup API. Then on startup check the database for corruption (using PRAGMA integrity_check or PRAGMA quick_check) and move to the backup if corruption is seen. -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
