From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from frost.carfax.org.uk ([85.119.82.111]:51579 "EHLO frost.carfax.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756125AbdGXVA6 (ORCPT ); Mon, 24 Jul 2017 17:00:58 -0400 Date: Mon, 24 Jul 2017 21:00:36 +0000 From: Hugo Mills To: Chris Murphy Cc: Cloud Admin , Btrfs BTRFS Subject: Re: Best Practice: Add new device to RAID1 pool Message-ID: <20170724210036.GK7140@carfax.org.uk> References: <1500895655.2781.6.camel@cloud.haefemeier.eu> <20170724204257.GJ7140@carfax.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="mMdCh5/a0q2ATNCM" In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: --mMdCh5/a0q2ATNCM Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Jul 24, 2017 at 02:55:00PM -0600, Chris Murphy wrote: > On Mon, Jul 24, 2017 at 2:42 PM, Hugo Mills wrote: > > > > > In my experience, it's pretty consistent at about a minute per 1 > > GiB for data on rotational drives on RAID-1. For metadata, it can go > > up to several hours (or more) per 256 MiB chunk, depending on what > > kind of metadata it is. With extents shared between lots of files, it > > slows down. In my case, with a few hundred snapshots of the same > > thing, my system was taking 4h per chunk for the chunks full of the > > extent tree. > > Egads. > > Maybe Cloud Admin ought to consider using a filter to just balance the > data chunks across the three devices, and just leave the metadata on > the original two disks? > > Maybe > > sudo btrfs balance start -dusage=100 It's certainly a plausible approach, yes. Or just wait it out -- the number of slow chunks is typically very small. Note that most of the metadata will be csums (which are fast), and not all of the other metadata chunks are slow ones. It would be interesting to know in this case the times of the chunks that have been balanced to date (grep for the lines with the chunk IDs in system logs). Hugo. -- Hugo Mills | Two things came out of Berkeley in the 1960s: LSD hugo@... carfax.org.uk | and Unix. This is not a coincidence. http://carfax.org.uk/ | PGP: E2AB1DE4 | --mMdCh5/a0q2ATNCM Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJZdl/zAAoJEFheFHXiqx3kf7QQALw2Ssf3wmRJwj7lKZV08Ga5 +nOEMv43D5dWZ2AvGsKK827mIQ2EyP3DhFPQFSfCri2SCH9ZukzrtOLv87CPZxgv 88Y8PW1t+gLKfYtowSDLWqD2iZNuFOX3hiOI4GP3FthDQ1RnOHRX/1zqgfffx3st AOe0wRpVEhqdp+IlfCVtM1QbVqJ1sFhIfhWaiy6ntAYAdB+anprY1nj4ueo62LP8 gDSWlMBlHIM++kBh3ew8zRG46JOlCKbvA5+pS9Z1tUXLy+Oe7rgPRrB1O7gtvusn hxz1WANBB68Ifo2IdmdFbVdoGhqecmI7exOo3qrfpk5EyfWlYr6MBacjgRxP81oI riBs57dW8cX3Kq6FeIfSXiA1rHpDgk1s1Il0IOUX3lrjiXQFi/f6gNmq+heNkdKG RcsCbZ5HV8dQqM0sOPXEUOzVO1fk2IeBxrDxlXi8IKF17zYs9qHbW99w1FdNP6ah l2P4Ep/RasyTjd4UNaGLuw5Fxm1NU+Ram725eidlYZVhNDL9jcY6izcu9Y7Ggjeq YRN5tnaM+o7yDaYJakj/U8CPwg/Y0Y4w7XbEUP24f/o0jUGUFybo0X7oS0w0/ZXU gdpU4yBzhHazXzaKznxrV/MExvY07xXHVftRFclyZ9tsW6TD2dYFx4WMTbFURtnf 5vMUShmSgxcsQ7ombYdE =+DWV -----END PGP SIGNATURE----- --mMdCh5/a0q2ATNCM--