[rrd-developers] striping - initial observations

[kevin brintnall]

On Wed, Oct 22, 2008 at 03:34:46PM +0100, Daniel.Pocock at barclayscapital.com wrote:
> > Then, it would make sense to set the stripe size to some 
> > multiple of a full row..  For some K:
> > 
> > 	strip_size = K * sizeof(rrd_value_t) * ds_cnt
> 
> 
> That makes sense - Ganglia has one ds per RRD, and 32 is a multiple of
> sizeof(rrd_value_t), so I believe this is fine.  I intend to make stripe
> size configurable rather than having a system for guessing it, and it
> will probably need to be a power of 2 to make the math efficient for
> finding the correct position in the file.

Lots of RRDs have more than one DS.  I don't think it's "guessing", since
the RRD geometry is known and fixed when it's installed into the stripe
file.

I can't think of any case where it would make sense to split a single RRD
row over more than one stripe.  The logic to make the stripe_size =
K*row_size should not be difficult.  Let's allow RRDTool to do the right
thing regardless of the RRD geometry...

That said, I am definitely for a config option to set "K".

-- 
 kevin brintnall =~ /kbrint at rufus.net/