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Thin provisioning and "discard" I/O requests

Nils Cant
Occasional Visitor

Thin provisioning and "discard" I/O requests

Hello,

we use thin provisioning on our P4000 cluster.
I noticed that Red Hat's GFS2 supports a "discard" mount option, that is meant to send "discard I/O requests" to the underlying hardware for blocks which have been freed.

Does anyone know if HP's P4000 systems support this feature? As it would be pretty cool to have thinly provisioned volumes be able to shrink as well.
2 REPLIES
Jitun
HPE Pro

Re: Thin provisioning and "discard" I/O requests

I don't think it would work.
Once data is written, the space is allocated by SANiQ on the SAN, even after its deletion.

Thin Provisioned Volumes can only grow, they will not shrink down.
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Nils Cant
Occasional Visitor

Re: Thin provisioning and "discard" I/O requests

Too bad. :/ But as GFS2 supports it, there must be SAN systems out there that can do it.

Or it's just very very new. :-) Anyway, I've tested it on an iscsi volume on our P4000, and it doesn't work.
Maybe it can be implemented in the future. Would definitely be very cool.