Cool! 2015-11-19 6:30 GMT+08:00 Wong, Steven <steven.w...@emc.com>:
> Regarding inquiry by Marica Antonacci on Wed, 18 Nov 2015 04:43:47 -0800 > > Failover scenarios are anticipated in the DVDI module and are being > tracked as this issue on github > https://github.com/emccode/mesos-module-dvdi/issues/23 > > The resolution of this issue requires that the underlying volume driver > supports a "pre-emptive mount" whereby any prior mounts are terminated > automatically by a mount from another node. > > Many but not all storage providers are capable of supporting this behavior. > > The intention is that DVDI will handle scenarios including: > > 1. Task crashes on an agent node and is rescheduled on a different node. > Note in this case, if the slave process remains running, it is very likely > that the dvdi module will remove the mount automatically now. However this > might not occur BEFORE the task is rescheduled on another cluster node, so > the upcoming pre-emptive mount feature could be useful in this scenario. > > 2. Entire Agent node crashes while task is running and does not restart or > return. The agent machine is a smoking piece of molten metal. This will > REQUIRE the new dvdi feature and support from the underlying storage driver. > > 3. Agent crashes and restarts. Similar to scenario #1 but perhaps the > unmounts takes longer. This scenario should result in removal of the > original mount upon restart, and is implemented now. If the Agent restart > takes a long time, the roadmap pre-emptive mount feature will be of value. > > As a related note, some storage providers and some filesystems actually > allow use of concurrent mounts from multiple cluster nodes, although this > is uncommon. The architecture of the dvdi module is intended to support > this, although no volume driver available today enable the functionality. > > > In summary pre-emptive mount is a roadmap feature for the dvdi module. I > expect it to be delivered shortly, after the feature is enabled in the > rexray driver. My best guess is that this will not occur within the next > two weeks, but it may occur within the next two months. > > > Steve Wong > Contributor to the Mesos dvdi module project Developer Advocate EMC{code} > - the open source advocacy group within EMC > > CODE OPEN, DEPLOY EVERYWHERE > https://github.com/emccode > blog.emccode.com > > 1.562.417.7048 > steven.w...@emc.com > @cantbewong > > -- Deshi Xiao Twitter: xds2000 E-mail: xiaods(AT)gmail.com
