On Fri, Nov 12, 2010 at 4:44 AM, Mike Fedyk <mfedyk@xxxxxxxxxxxxx> wrote: > On Thu, Nov 11, 2010 at 11:41 PM, Josef Bacik <josef@xxxxxxxxxx> wrote: >> On Fri, Nov 12, 2010 at 05:47:14PM +1100, Chris Samuel wrote: >>> On 11/11/10 23:52, Josef Bacik wrote: >>> >>> > This feature incurs a performance penalty in larger filesystems, it is >>> > recommended for use with filesystems of 1 GiB or smaller. >>> >>> Maybe slightly stronger, for example: >>> >>> This feature incurs a performance penalty for larger filesystems and it >>> is ONLY recommended for use with filesystems of 1 GiB or smaller. >>> >>> Is it worth having a check and a warning printed if a user does >>> try and make a filesystem larger than 1GiB with this option ? >>> >>> Just in case they don't RTFM... >>> >> >> No because depending on your usage it's actually kind of usefull for anything >> less than 5 GiB, and you're only looking at about a 5-10% perf degredation when >> using it on larger filesystems. Thanks, >> > > Then a warning of 10% slowdown if > 10GB would be good. It's > surprising how many will just read some forum post and not concern > themselves with the docs at all. > > And making them type "yes" if > 100GB is probably a good idea too... > Just for clarification, you'll probably see a ~5-10% slowdown for any size partition, not just "if > 10 GB" But for smaller filesystems (~<5 GiB), you may want to accept the performance penalty for more efficient disk space utilization. For really small filesystems (~<1 GiB), using Btrfs defaults can really start to impact on space utilization. So the parent data+metadata patch currently forces the data+metadata option on <1 GiB. The Wiki is probably a better place for more extensive discussion of the merits and trade-offs of this option. The user still needs to actively "opt-in" to this option (unless their partition is < GiB), and the man page will indicate a performance penalty is incurred. For something as important as changing your filesystem default settings, it seems fair to expect the user has done their homework when changing from the default setting. -- 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
