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
On Jun 05, 2007 18:47 -0400, Tod Hagan wrote:> 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.Not really. We submitted a patch to clarify this, so the "stride=" value is the number of blocks on a SINGLE disk. This ensures that the bitmaps are round-robined across all disks.> 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?-E stride=16, based on 64k / 4k Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.