gjournal alignment on 4K sector advanced format drives

[Carl]

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