From: Mike Mestnik <cheako911@gmail.com>
To: linux-ext4@vger.kernel.org
Subject: Re: How to use mkfs.ext4 "stride=" on RAID correctly?
Date: Wed, 13 Jan 2010 18:58:46 -0600 [thread overview]
Message-ID: <fa7b26051001131658ya96c3b0ieb6010c6fba389c4@mail.gmail.com> (raw)
In-Reply-To: <fa7b26051001131613jc61e20fu5e4d0ccee86d6b16@mail.gmail.com>
On Wed, Jan 13, 2010 at 6:13 PM, Mike Mestnik <cheako@visi.com> wrote:
> What should this value be? From what I gather it should be the length
> of data stored on a single disk for each RAID level block. If that's
> the case how is it that two given data blocks are calculated to be on
> separate drives? It seams to me that the stripe-width is also
> essential in this regard, but the man page does not reflect this.
>
> For example let's say that stride=1, then which of the following
> blocks are not on the same drive as 1: 8 9 10?
> The answer is dependent on the number data disks, like so.
> Where x = n - 1 or n depending on the RAID type.
> if x = 2 then 9
> if x = 3 then 8 and 10
> if x = 5 then 8 and 9
>
Wait!!
I got this all wrong, one would need all of x, n, and stride to
successfully determine the disk used for a given stride.
Seams to me mkfs is missing some parameters. What about [-g
blocks-per-group]...
http://tldp.org/HOWTO/Software-RAID-0.4x-HOWTO-8.html
> There is no way to make this calculation with out knowing x, further
> more calculating x based of of both stride and stripe-width is round
> about... Why not simply ask for x, the number of data disks and have
> stripe-width be the value that is calculated, as stride might not go
> into stripe-width evenly leaving you with a headache.
>
> Did I locate a bug?
>
> Is there a better forum for this discussion?
>
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next prev parent reply other threads:[~2010-01-14 0:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-14 0:12 How to use mkfs.ext4 "stride=" on RAID correctly? Mike Mestnik
2010-01-14 0:13 ` Mike Mestnik
2010-01-14 0:58 ` Mike Mestnik [this message]
2010-01-15 17:51 ` Ric Wheeler
2010-01-16 2:59 ` Mike Mestnik
2010-01-16 5:38 ` Martin K. Petersen
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