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Re: discard and wapbl



Roy Marples <roy%marples.name@localhost> writes:

> Should wapbl be set in DOM0, DOMU or both?

I set it in both.  Not really about xen, but I guess the useful answer
is that whether to use it is that it isn't about xen.  I even have it
set in the dom0 that has regular files backing the xbd used by the domU.

> Ditto for discard (SSD TRIM) support when the storage is LVM? Guessing
> only DOM0 here.

I'm less clear on this, but it would seem to make sense on the dom0,
which actually has disks.  The domU just sees xbd(4) instances, and the
reads/writes are forwarded to something in the dom0.

But, is this about a filesystem?  With the normal Xen setup, the
filesystem code runs in the domU, and does opertaions to xbd, which then
forwards them.   So if discard causes TRIM from the filesystem, we'd
have to have a virtual TRIM operation in xbd, and that would have to
forward a corresponding real TRIM operation.  I have never heard of this
being implemented, but I have also not read the driver.


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