On 01/13/2010 07:58 PM, Mike Mestnik wrote:
On Wed, Jan 13, 2010 at 6:13 PM, Mike Mestnik<cheako@xxxxxxxx> 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
Hi Mike,
Recent changes upstream export alignment and optimal IO size for you (at
least for software RAID/dm devices) and for some external arrays if the
vendor exports the information in a standard way.
Martin was the lead on that & work has been ongoing to add support up
the tool chain.
Hopefully, this will get easier to do so we all don't have to work out
the numbers each time we build on RAID :-)
Ric
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?
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
