gjournal alignment on 4K sector advanced format drives
Jeremy Chadwick
freebsd at jdc.parodius.com
Wed Sep 1 09:19:21 UTC 2010
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 |
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