Date: Wed, 1 Sep 2010 02:19:19 -0700 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Carl <k0802647@telus.net> Cc: freebsd-fs@freebsd.org Subject: Re: gjournal alignment on 4K sector advanced format drives Message-ID: <20100901091919.GA98434@icarus.home.lan> In-Reply-To: <4C7E18CB.7020400@telus.net> References: <4C7CE2D0.40400@telus.net> <4C7E18CB.7020400@telus.net>
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On Wed, Sep 01, 2010 at 02:11:39AM -0700, Carl wrote: > On Tue Aug 31 12:19:52 UTC 2010, Ivan Voras wrote: > >On 08/31/10 13:09, Carl wrote: > >>Now I want to add gjournal to some of my partitions. It seems to me that > >>I must also ensure the journal is aligned just as I've done with the > >>data. So far, though, I have found no information as to how the > >>journal's own filesystem layout works. Does it use fixed size > >>blocks/fragments like the UFS2 data does? If so, what is its minimum > >>addressable unit size? If it is smaller than 4KiB, we get journal > >>misalignment and a performance loss, right? What must I do to ensure the > >>journal is fully aligned? > > > >gjournal writes its metadata throughout the journal in sector sizes (512 > >bytes) so it cannot be aligned in this way. > > > >For this you need a solution which will actually change the sector size, > >like gnop or my glabel patch. > > From the following discussion, the glabel patch isn't likely to get > committed, in which case I can't use it: > > http://comments.gmane.org/gmane.os.freebsd.devel.hackers/40664 > > Correct me if I'm wrong, but the gnop solution is still > non-persistent and therefore unavailable for partitions whose > mounting cannot be delayed till after startup scripts have executed. > I'm not knowledgeable enough about this, so I'd welcome a clear > description of how to reliably and automatically use gnop to > override sector size at boot time. > > It sounds like neither ZFS nor gjournal are suitable for a > production server with WDxxEARS drives. Soft updates and horribly > long fsck times is the only option? > > A pox on Western Digital for delivering drives that lie about sector > size >:-< Can't you just set the jumper on the drive to us 512-byte sectors? I mean, that's what it's there for... -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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