Date: Wed, 29 Oct 2008 09:47:32 +0000 From: Dr Josef Karthauser <joe@tao.org.uk> To: Peter Schuller <peter.schuller@infidyne.com> Cc: Zaphod Beeblebrox <zbeeble@gmail.com>, Daniel Jameson <DJameson@emerytelcom.com>, freebsd-current@freebsd.org Subject: Re: ZFS attaching direct access drives as Scsibus#target#drive# Message-ID: <49083134.9050701@tao.org.uk> In-Reply-To: <20081017175424.GA73168@hyperion.scode.org> References: <0A8710FF880BBB4687AEC66F9DCF7D0C26B462@SERVER1.emerytelcom.com> <5f67a8c40810142200o6074cd42hec0ff6f2b87d3648@mail.gmail.com> <20081017175424.GA73168@hyperion.scode.org>
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Peter Schuller wrote: >> glabel can have some funny effects due to the geom taste order. If >> something is part of a mirror (for instance) and the label tastes before the >> mirror, I've seen items of the mirror come up with glabel instead of >> attaching to the mirror. > > Does gmirror perhaps keep meta-data at the beginning of the underlying > device? > > Something which can easily happen is that you have, for example, a > slice covering the entire device (exactly the entire device). You then > glabel the slice, and when you reboot the underlying device is labeled > instead of the slice. Similar issues can happen in other cases, such > as glabel:ing an iSCSI target on another host, if that iSCSI target is > backed by, for example, a zvol. > > For these reasons I always make sure that the "contained" device ends > earlier than the "containing" device (and the other way around). This > way there is never any GEOM (disk, slice, partition, glabel, gmirror, > etc) which starts or ends at the exact same spot as another GEOM. This > removes the ambiguity. > > At least this is my interpretation of the situation; I haven't gone > and proven it. The meta data is kept at the end of the device; I always use the -h flag when labelling to get around this problem, as it records the name of the "contained" device in the meta block and never gets confused that way. Joe
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