On 12/19/07, Michal Soltys [off-list ref] wrote:

Justin Piszcz wrote:

quoted

Or is there a better way to do this, does parted handle this situation
better?

What is the best (and correct) way to calculate stripe-alignment on the
RAID5 device itself?


Does this also apply to Linux/SW RAID5?  Or are there any caveats that
are not taken into account since it is based in SW vs. HW?

---

In case of SW or HW raid, when you place raid aware filesystem directly on
it, I don't see any potential poblems

Also, if md's superblock version/placement actually mattered, it'd be pretty
strange. The space available for actual use - be it partitions or filesystem
directly - should be always nicely aligned. I don't know that for sure though.

If you use SW partitionable raid, or HW raid with partitions, then you would
have to align it on a chunk boundary manually. Any selfrespecting os
shouldn't complain a partition doesn't start on cylinder boundary these
days. LVM can complicate life a bit too - if you want it's volumes to be
chunk-aligned.

That, for me, is the next question - how can one educate LVM about the
underlying block device such that logical volumes carved out of that
space align properly - many of us have experienced 30% (or so)
performance losses for the convenience of LVM (and mighty convenient
it is).


-- 
Jon