Neil Brown wrote:
[]
raid5 shouldn't need to merge small requests into large requests.
That is what the 'elevator' or io_scheduler algorithms are for. There
already merge multiple bio's into larger 'requests'. If they aren't
doing that, then something needs to be fixed.
It is certainly possible that raid5 is doing something wrong that
makes merging harder - maybe sending bios in the wrong order, or
sending them with unfortunate timing. And if that is the case it
certainly makes sense to fix it.
But I really don't see that raid5 should be merging requests together
- that is for a lower-level to do.
Hmm. So where's the elevator level - before raid level (between e.g.
a filesystem and md), or after it (between md and physical devices) ?
I mean, mergeing bios into larger requests makes alot of sense between
a filesystem and md levels, but it makes alot less sense to do that
between md and physical (fsvo "physical" anyway) disks.
Thanks.
/mjt
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
