Date: Wed, 01 Sep 2010 02:11:39 -0700 From: Carl <k0802647@telus.net> To: freebsd-fs@freebsd.org Subject: Re: gjournal alignment on 4K sector advanced format drives Message-ID: <4C7E18CB.7020400@telus.net> In-Reply-To: <4C7CE2D0.40400@telus.net> References: <4C7CE2D0.40400@telus.net>
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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 >:-< Carl / K0802647
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