Date: Thu, 31 Aug 2017 15:26:23 +0100 From: Frank Leonhardt <frank2@fjl.co.uk> To: freebsd-questions@freebsd.org Subject: Re: help creating new gmirror > 2TB Message-ID: <59A81C8F.9020002@fjl.co.uk> In-Reply-To: <alpine.BSF.2.21.1708301856210.93591@wonkity.com> References: <CAFsnNZLeuLYEJVozsoSvDtvgfMf4UueJhm37waOQ5_kyxs-rhg@mail.gmail.com> <26f5e88e-1ea7-6332-ca5e-f055cfbdd280@fjl.co.uk> <alpine.BSF.2.21.1708301856210.93591@wonkity.com>
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On 31/08/2017 01:59, Warren Block wrote: > On Wed, 30 Aug 2017, Frank Leonhardt wrote: >> Trying to get geom mirror to work with GPT as it stands just leads to >> pain. I've taken a look at the code with a view to fixing this is no >> one else does, but UFS is so un-cool in most circles and I don't >> fancy doing it alone in case I zap someone's data. it doesn't look >> that tricky to move the metadata somewhere else, and by checking for >> a GPT you can select between the old/new block. It's unexpected >> interactions I'm worried about. > > At some point in the last couple of years, hrs@ produced a working > patch which did something like that, although I don't remember the > details. It moved either the GPT backup table or the gmirror > metadata. It was turned down as breaking standards. I remember something like this too - if you turn it up please point me at it! I have a feeling that it moved the GPT backup for some reason. Moving the mirror metadata would make more sense, but I assume this was tricky for some reason. I think there's a good argument for a geom mirror2, designed to work with GPT. IME ZFS isn't the universal answer to everything thanks to CoW, random-access R/W files and fragmentation. Until the fragmentation issue can be addressed (e.g. with a defragger) databases and VM images are going to run badly. Another answer would be for a FS to access it at vdev level (i.e. just use the volume manager aspect). At the moment it's a CoW dataset or a CoW dataset. I'd assumed Oracle would have addressed this, given their interest in databases. Regards, Frank.
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