----- Original Message ----- > From: "Lalatendu Mohanty" <lmohanty@xxxxxxxxxx> > To: "Dan Lambright" <dlambrig@xxxxxxxxxx>, "Gluster Devel" <gluster-devel@xxxxxxxxxxx> > Sent: Monday, October 20, 2014 11:28:28 AM > Subject: Re: Gluster tiering feature > > On 10/18/2014 01:11 AM, Dan Lambright wrote: > > Myself, Joseph Fernandez, and others have been working on a tiering feature > > for gluster. We are in the prototype phase and demoed some code recently > > internally to Red Hat. In its first incarnation it resembles the server > > side cache tier Ceph has, or dm-cache in the kernel. So, fast storage and > > slow storage are exposed as a single volume, data that is frequently used > > makes its way to fast storage, and the system responds dynamically to > > changing usage. Because migration between tiers is time consuming, a cache > > tier is a good fit for workloads where the set of hot data is stable. A > > cache tier can be added or removed at run-time. The tiering logic is very > > general-purpose infrastructure, and can be used for elaborate data > > placement graphs or other data migration features. > > > > The design is in early stages.. but current thinking can be found on the > > feature page and the links below, and all the code is on the forge. > > > > http://www.gluster.org/community/documentation/index.php/Features/data-classification > > > > goo.gl/bkU5qv > > > > Thanks, > > Dan > > _______________________________________________ > > Gluster-devel mailing list > > Gluster-devel@xxxxxxxxxxx > > http://supercolony.gluster.org/mailman/listinfo/gluster-devel > > Looks awesome!! Thanks for putting these docs. > > However I have a few questions on the following. > /"Current thinking is a snapshot cannot be made of a volume with a cache > tier, however a cache may be "detached" from a volume and then a > snapshot could be made//"./ > > As far as I can understand, detaching cache tier will take a good amount > of time (of course it depends on the amount of data), so detaching the > cache tier and then taking snapshot will be time consuming and might not > be used much (from a user point of view) . However I am wondering if > pausing cache is less expensive then detaching cache? Also does pause > cache migrates all data from hot to cold subvol, or just from that time > onwards? > > Thanks, > Lala yes, the thinking is "pausing" the cache would demote all the data off the fast tier. I think getting snap to work with this is a stretch goal, at least in the beginning. I'm worried about thorny issues that may happen. For example, suppose someone snapped a tiered volume, then detached the fast tier, the tried to restore the volume. > _______________________________________________ Gluster-devel mailing list Gluster-devel@xxxxxxxxxxx http://supercolony.gluster.org/mailman/listinfo/gluster-devel
