From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mitch Harder Subject: Re: Btrfs-progs: Update man page for mixed data+metadata option. Date: Fri, 12 Nov 2010 09:59:32 -0600 Message-ID: References: <1289412138-8049-1-git-send-email-mitch.harder@sabayonlinux.org> <20101111021034.GA6911@dhcp231-156.rdu.redhat.com> <20101111125229.GA10179@dhcp231-156.rdu.redhat.com> <4CDCE2F2.5020500@csamuel.org> <20101112074105.GD10179@dhcp231-156.rdu.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: Josef Bacik , Chris Samuel , linux-btrfs@vger.kernel.org To: Mike Fedyk Return-path: In-Reply-To: List-ID: On Fri, Nov 12, 2010 at 4:44 AM, Mike Fedyk wrot= e: > On Thu, Nov 11, 2010 at 11:41 PM, Josef Bacik wrot= e: >> 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 an= d 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 degre= dation when >> using it on larger filesystems. =A0Thanks, >> > > Then a warning of 10% slowdown if > 10GB would be good. =A0It'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. =46or 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. =46or 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html