Re: RAIDframe and alignment on 4K-sector disks?

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

On Tue, 13 Jun 2017, John D. Baker wrote:

> On Tue, 13 Jun 2017, Patrick Welche wrote:
> 
> > > Doesn't RAIDframe assume 512-byte sectors?  So, 64k stripe size would
> > > be SecPerSU=128, yes?
> > 
> > I think it's SecPerSU=64 blocks = 32k. Two data disks in one write, so
> > 2 * 32k = 64k = MAXPHYS written in one write.
> > 
> > (Please correct me if I'm wrong: I just make a 3 * 2T raid 5 this
> > morning ;-) )

Clarification from mlelstv, prompting me to re-read "raidctl(8)" more
closely shows where I got confused:

  StripeUnit (SU) == data component (disk)

This is what I'd misunderstood the whole time.

It turns out the 2TB disks for the planned RAID-5 also have 512-byte
native sectors, not 4K sectors.  So no alignment constraints after all.

I have a 3-disk RAID-5 across substantially smaller disks (with native
512-byte sectors) whose configuration I shall have to revisit.
Fortunately, its contents are easily expendable for testing.

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