Calculating stride values?

[Tod Hagan <tod gust sr unh edu>]

All,

I have a question about calculating the value for the -E stride option
to mke2fs.

The mke2fs man page says

      stride=stripe-size
             Configure the filesystem for a RAID array with stripe-size filesystem blocks per stripe.

So stride = size of stripe/blocksize.

The size of a stripe is the RAID chunk size * the number of drives in the RAID.

My question: are parity disks included in the number of drives, or are
only data drives counted?

For example, take the example of six drives configured for RAID 5 with a
chunk size of 64 and a 4K blocksize:

1. Parity drive included: 64*6/4 = 96
2. Parity drive excluded: 64*5/4 = 80

Which is correct?

Thanks.

Tod

-- 
Tod Hagan
Information Technologist
AIRMAP/Climate Change Research Center
Institute for the Study of Earth, Oceans, and Space
University of New Hampshire
Durham, NH 03824
Phone: 603-862-3116