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Re: Calculating stride values?



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.


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