[sheepdog-users] [sheepdog] qustions about sheepdog presentation

Valerio Pachera sirio81 at gmail.com
Wed Oct 22 11:15:49 CEST 2014

2014-10-22 11:02 GMT+02:00 Vasiliy Tolstov <v.tolstov at selfip.ru>:
> Hi.
> I find this slides
> http://sheepdog.github.io/sheepdog/_static/sheepdog-openstack.pdf
> Page 9 contains gateway node with shared cache on ssd. What data
> placed on this ssd ?

qemu sends a read request;
sheep request from the other nodes the required object;
it stores a copy of that object in the object cache (ssd);
the next time qemu is sending a read request for the same object, it
will read it directly from it's ssd.

Qemu sends a write request;
sheep write a new object in the object cache (ssd) instead of writing
that on other nodes;
after a certain amount of time, it's going to replicate this object on
the other nodes ad remove it from the cache.

It's evident that if the node dies before replicating the object in
the cache, you loose data.

Object cache isn't well tested yet, so I suggest not to use it in
production but please test it and report any issue you may find.

Thank you.

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