gjournal alignment on 4K sector advanced format drives

[Jeremy Chadwick]

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 at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |