Namhyung Kim [off-list ref] writes:
2011-06-15 (수), 08:51 +0200, Keld Jørn Simonsen:
quoted
On Wed, Jun 15, 2011 at 11:02:00AM +0900, Namhyung Kim wrote:
quoted
If @conf->far_offset > 0, there is only 1 stripe so that we can treat
the array same as 'near' arrays.
does it also work with more than 2 copies - eg 3 copies?
I think the original code just takes the available data blocks with the
lowest address.
Hi,
Let me clarify this: AFAIK, 'far offset' array saves redundant data in
the diagonally adjacent chunk/disk, so it could be roughly thought as
'raid0' array with reduced size - just ignore redundant chunks here. It
was my mistake considering it as 'near' array. :(
I'm confused again. If fo > 0 && fc > 1 && nc > 1 then it turns out to
a near array with reduced size, no? Does it still need to be treaded
as RAID0?
Therefore, it makes more sense distributing reads over the array based
on some criteria - here, the address of starting sector - like RAID0
does. Now I see that the same goes to the 'far copies' array exactly, so
the original code is correct.
Thanks.
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On Wed, 15 Jun 2011 23:35:53 +0900 Namhyung Kim [off-list ref] wrote:
Namhyung Kim [off-list ref] writes:
quoted
2011-06-15 (수), 08:51 +0200, Keld Jørn Simonsen:
quoted
On Wed, Jun 15, 2011 at 11:02:00AM +0900, Namhyung Kim wrote:
quoted
If @conf->far_offset > 0, there is only 1 stripe so that we can treat
the array same as 'near' arrays.
does it also work with more than 2 copies - eg 3 copies?
I think the original code just takes the available data blocks with the
lowest address.
Hi,
Let me clarify this: AFAIK, 'far offset' array saves redundant data in
the diagonally adjacent chunk/disk, so it could be roughly thought as
'raid0' array with reduced size - just ignore redundant chunks here. It
was my mistake considering it as 'near' array. :(
I'm confused again. If fo > 0 && fc > 1 && nc > 1 then it turns out to
a near array with reduced size, no? Does it still need to be treaded
as RAID0?
This would be a mix of near and offset. I'm not at all sure what the "best"
read balancing approach would be. But as I don't think anyone would ever
actually use it, I don't think it really matters.
Thanks,
NeilBrown
quoted
Therefore, it makes more sense distributing reads over the array based
on some criteria - here, the address of starting sector - like RAID0
does. Now I see that the same goes to the 'far copies' array exactly, so
the original code is correct.
Thanks.
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