On Sat, Mar 20 2010 at 8:03pm -0400, Olivier B. <dm.list@xxxxxxxxx> wrote: > Hi, > > I'm looking at the dm-cache module from Ming Zhao ( > http://users.cis.fiu.edu/~zhaom/dmcache/index.html ), and would like > to know if there is a problem to include it upstream. > > It looks stable for a while, and some people seem to use it in production. Such a DM target would be quite useful to have upstream given how prevalent SSDs have become. Other work has been a priority but a caching DM target is definitely on the TODO. If others can help take steps to make a robust caching DM target a reality then we should be able to get an implementation upstream sooner rather than later. Just curious: where have you gotten this insight about dm-cache being stable and used in production? That should help dm-cache's cause if it is submitted for review. Seems Ming posted dm-cache to dm-devel (as a large monolithic patch) on 8/24/07. dm-cache would need to be rebased to the latest upstream kernel.org kernel (e.g. Linux >= 2.6.34-rc1). Ideally dm-cache would be resubmitted to dm-devel incrementally such that basic infrastructure is introduced in early patches and more advanced capabilities (e.g. writeback) follow in later patches. Each patch should have a corresponding patch header the documents what the patch provides. Writeback support is arguably the most useful aspect of a caching DM target so emphasis must be placed on its review/implementation. Using SSD as a persistent writeback cache should afford us much more fault tolerance in the face of system crashes during writeback to the slower media. I know Heinz has taken steps to implement a caching DM target. So reconciling dm-cache's design and implementation with what Heinz has would be a worthwhile component of the dm-cache review (assuming Heinz's implementation is also posted for review). Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
