gjournal alignment on 4K sector advanced format drives

[Carl]

My understanding is that I can avoid misalignment-induced performance 
problems with Western Digital WDxxEARS drives (4KiB physical sector 
size) by ensuring two things:

1. GPT partitions are aligned to 4KiB boundaries, and

2. Use "newfs -b 32768 -f 4096 ..." so that UFS2 fragments are not 
smaller than the physical sector size.

True?

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?

In the past I've put the data and journal on the same provider, but I am 
unsure whether a specified size for the journal is accurately observed. 
If I specify a 1GiB journal, will I get exactly that? My concern is 
whether an added/subtracted sector might be used for some kind of 
journal header, thereby throwing off the alignment of the journal again.

Is it better to put the journal on its own provider (ie. separate 
partition) to aid alignment in some way? What are the pros and cons for 
shared vs. separate providers in general?

Carl                                             / K0802647