> It's actually not possible in general. Since it's possible to have > different bits of the FS (data vs metadata) with different replication > levels, one byte written to the FS could take up either 1 or 2 bytes > of raw disk storage, and there's no way of predicting what the overall > usage will be, so it's not possible to give an accurate estimate of > free space. > > Similarly, if you have a 10G subvolume, and a snapshot of it, then > how much space does each one take up? Yes, I agree it is not simple However, the lvs command from LVM does provide a useful way to show how full a snapshot volume is. In the btrfs situation, the snapshot is within the FS, so it is not quite the same metric I am looking at what metrics are needed to monitor btrfs in production. I actually look after the ganglia-modules-linux package, which includes some FS space metrics, but I figured that btrfs throws all that out the window. Can you suggest metrics that would be meaningful, do I look in /proc or with syscalls, is there any code I should look at for an example of how to extract them with C? Ideally, Ganglia runs without root privileges too, so please let me know if btrfs will allow me to access them -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
