From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: ddf: remove failed devices that are no longer in use ?!? Date: Tue, 30 Jul 2013 11:34:35 +1000 Message-ID: <20130730113435.3421a111@notabene.brown> References: <51F2E4B9.1020505@arcor.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/=50IKXbN=H2Hv/pr5V0zP2V"; protocol="application/pgp-signature" Return-path: In-Reply-To: <51F2E4B9.1020505@arcor.de> Sender: linux-raid-owner@vger.kernel.org To: Martin Wilck Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/=50IKXbN=H2Hv/pr5V0zP2V Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 26 Jul 2013 23:06:01 +0200 Martin Wilck wrote: > Hi Neil, >=20 > here is another question. 2 years ago you committed c7079c84 "ddf: > remove failed devices that are no longer in use", with the reasoning "it > isn't clear what (a phys disk record for every physically attached > device) means in the case of soft raid in a general purpose Linux compute= r". >=20 > I am not sure if this was correct. A common use case for DDF is an > actual BIOS fake RAID, possibly dual-boot with a vendor soft-RAID driver > under Windows. Such other driver might be highly confused by mdadm > auto-removing devices. Not even "missing" devices need to be removed > from the meta data in DDF; they can be simply marked "missing". >=20 > May I ask you to reconsider this, and possibly revert c7079c84? > Martin You may certainly ask .... I presumably had a motivation for that change. Unfortunately I didn't reco= rd the motivation, only the excuse. It probably comes down to a question of when *do* you remove phys disk records? I think that if I revert that patch we could get a situation where we keep adding new phys disk records and fill up some table. We should probably be recording some sort of WWN or path identifier in the metadata and then have md check in /dev/disk/by-XXX to decide if the device has really disappeared or is just failed. Maybe the 'path' field in phys_disk_entry could/should be used here. Howev= er we the BIOS might interpret that in a specific way that mdadm would need to agree with.... If we can come up with a reasonably reliable way to remove phys disk records at an appropriate time, I'm happy to revert this patch. Until then I'm not sure it is a good idea..... But I'm open to being convinced. Thanks, NeilBrown --Sig_/=50IKXbN=H2Hv/pr5V0zP2V Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iQIVAwUBUfcYKznsnt1WYoG5AQJ/bw/7BqEYBgSysvhnKr4/w4T47BMByZTyuipY ZInnUPM7y4vo2P2LR2wMo71e9sEM0xECpgxo0j+QZzQ0Aykt5FglFUJHS5mnYosH J9XoUx3NXknYNINYnd57r4JTWHJeoa7zRO5OEgZ6r72qFu3jsFyrieINs6/surO5 raQjMbq7G0QIIFhx+Ox8uAVn5kLJe6uzQGvrdFLAHrF5cjXOhOZ2R+MpR6aVnRM/ Ji6QIawtt67jEmziF/5q+SpgBQ82LQqKbZ6Gd0NQzVrVunS+yeH6QvvLoXRZ2WFO 0xEyqDkDCThAIQQpnxYzP8pMMGcWcjtiMwh9NiC3d4JMq3ZITV1mURS0ktTKn7o/ d2OgMM61/AyktyJZ7K4XgqV0XEaZcHXP+a5iZbxtodkJiURR2rPnOH/IsqVSZc0L sWFE7ZHPd/rJB0XXNgFLTWMkDu+6bYIs1uEKobPESyGQHGF4KKmYC8rR2flcgohx wKsejTMbagiU4NIbUNmm6e9TlC54ty5barl7NHJxeIfQp4QJqHOBCXjlA0kOD3fN S/vOusZ/1WtpCDm3osmiVmBpQxVhGD908mK3zmQRVS/FAmzkSGlqkR+5zKdIHivY EDKa5fleljqy54kXVVOY65imTX5WJ5Z2HwmiN0SdfNec7cytabvKoUr0JFPb/3cf UpR2v7m3toY= =xm1c -----END PGP SIGNATURE----- --Sig_/=50IKXbN=H2Hv/pr5V0zP2V--