[dm-devel] striped targets with LVM2 logics
EXT / DEVOTEAM VAROQUI Christophe
ext.devoteam.varoqui at sncf.fr
Fri Jul 25 04:37:01 UTC 2003
Hello,
I would like to raise the issue of striped target logics with LVM2 :
With the current stable release, one can set the number of stripes at LV
creation time.
Then pvmove is allowed to move a stripe to a PV that already host a stripe
of the same LV,
thus killing the performance for this LV and for every other LV hosted on
this PV.
I guess you are already aware of that pb,
and would like to know what policy you intend to implement to resolve this
issue.
I wish one can just bypass the nb of stripes setting and let LVM2 decide
what mapping would give the best perf.
Maybe adding a "-mi / --min-stripes" and a "-Mi / --max-stripes" could give
useful input to the algorithm.
A default max-stripes value of 5 or 6 seems to be standard (for storageworks
firmware at least)
Then pvmove logics should check if a segment is available on a PV that do
not host a stripe for this LV.
If there is none, then reduce the number of stripes for this LV.
regards,
cvaroqui
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