From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Steigerwald Subject: Re: speeding up slow btrfs filesystem Date: Sat, 17 Dec 2011 12:09:56 +0100 Message-ID: <201112171209.56877.Martin@lichtvoll.de> References: <201112161851.52011.Martin@lichtvoll.de> <201112162158.45819.Martin@lichtvoll.de> <20111217100302.6beffbcd@sf.vba.domain> (sfid-20111217_102134_745546_A2A977B8) Mime-Version: 1.0 Content-Type: Text/Plain; charset=utf-8 Cc: linux-btrfs@vger.kernel.org To: Sergei Trofimovich Return-path: In-Reply-To: <20111217100302.6beffbcd@sf.vba.domain> List-ID: Am Samstag, 17. Dezember 2011 schrieb Sergei Trofimovich: > On Fri, 16 Dec 2011 21:58:45 +0100 >=20 > Martin Steigerwald wrote: > > Nope. Doesn=C2=B4t seem to help much. > >=20 > > How to turn it off, after turning it on? > >=20 > > deepdance:~> LANG=3DC mount -o remount,datacow / > > mount: / not mounted already, or bad option >=20 > In debian you can disable syncing on per-process basis: > http://packages.debian.org/sid/eatmydata >=20 > $ eatmydata apt-get install foo > $ eatmydata firefox > $ eatmydata liferea >=20 > makes things more bearable I am not ready to accept that this is the proper answer to what I=20 experience. Applications using fsync() are realistic real world scenari= os=20 and I think BTRFS has to cope with that. Yesterday I upgraded the laptop to 3.2-rc4. After converting the inode=20 cache the filesystem appeared to be faster, but I have to wait for some= =20 Debian packages to pile up on the repository servers to get a real=20 impression. I think I will scrub / balance / defragment the filesystem after a back= up.=20 But I am not sure in what order. I understand that defragment defragments files. But then what does bala= nce=20 do? For RAID setup I have seen it distributing data evenly across drive= s=20 when I echo > /sys/block/sda/[=E2=80=A6]/delete a drive before and BTRF= S had to=20 distribute unevenly cause of that. But what does it do on a filesystem = on a=20 single drive? I bet it would balance out trees? Will it resize trees wi= th=20 lots of unused space as well? According to deepdance:~> btrfs filesystem df /=20 Data: total=3D11.23GB, used=3D6.98GB System, DUP: total=3D8.00MB, used=3D4.00KB System: total=3D4.00MB, used=3D0.00 Metadata, DUP: total=3D1.86GB, used=3D511.35MB deepdance:~> btrfs filesystem show [=E2=80=A6] Label: 'debian' uuid: 2bf5b1dc-1d89-4f0d-a561-1a5551a27275 Total devices 1 FS bytes used 7.48GB devid 1 size 15.00GB used 14.97GB path /dev/dm-0 Btrfs Btrfs v0.19 the filesystem might have had some chances to fragment heavily, cause t= he=20 tree sizes add up almost to the 15 GB of space available. I also remember that for some time the filesystem was nearly full which= =20 would explain the tree sizes. Ciao, --=20 Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- 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