Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
(Follow-up question below. Apologies for the inconsistent quoting style. I don't know how to force Outlook to do more consistent quoting.) -----Original Message----- From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of Roland Kammerer Sent: Tuesday, December 05, 2017 1:17 AM To: drbd-user at lists.linbit.com Subject: Re: [DRBD-user] (newbie question) DRBD 9, pure controller without data storage On Mon, Dec 04, 2017 at 11:10:16PM +0000, Riches Jr, Robert M wrote: > (This is a newbie question.) > > Having got non-LVM version 9 drbdadm working with two storage nodes > and a few no-local-storage nodes, I'm attempting to graduate to using > drbdmanage and LVM. My goal is to have two storage nodes, one pure > controller node without data storage, and a few no-local-storage > compute nodes. However, I don't understand the green box in Figure 5 > in the User's Guide, labeled as a 'Control node', 'controlvolume is a > local LV', 'pure Controller', and 'nodes without data storage'. This is the figure: > > https://docs.linbit.com/ug-src/users-guide-9.0/images/drbdmanage-venn. > png > > The only LVM volume group I see mentioned in chapter 5 of the DRBD 9 > UG is the one it suggests to name 'drbdpool'. However, if the pure > controller has no data storage, how can the controlvolume be a local > LV. Can someone please enlighten a newbie on what seem to be contradictory descriptions? There are two types of storage drbdmange can use: - the control volume (which is the cluster wide database, 2x4MB, always on thick LVM) - the storage for your actual DRBD resources (LVM/ZFS thin/thick). That makes 4 combinations: - The node has a copy of the control volume, that makes it a "control node". It can then provide storage for DRBD resources or not (control node or pure controller). A use case for a pure controller might be a "quorum node" that just has a copy of the cluster DB. Let's say you have 3 nodes, one of them is a pure controller, one of the other nodes fails then the cluster can continue as it still has 2 nodes with a copy of the control volume. - The node does not have a copy of the cluster DB and gets its cluster DB from another node via TCP. These are satellites. They can have local storage for DRBD resources or not. Regards, rck -----End Of Original Message----- Thank you for that explanation/clarification. I think I understand now. Let me make sure my understanding is correct, especially concerning the size and contents of the VGs: - A "quorum node" will have a VG named 'drbdpool' that needs only enough space for the control volume. It will be added by doing "drbdmanage add-node --no-storage <nodeName> [IPaddress]" - Each other "control node" will have a VG named 'drbdpool' with enough space for the control volume _and_ the DRBD resources. It will be added by doing "drbdmanage add-node <nodeName> [IPaddress]" (no options). - A "pure client" node will have _no_ VG. It will be added by doing "drbdmanage add-node --satellite --no-storage <nodeName> [IPaddress]". - If I determine that an external node is one of the droids I'm looking for, it will have _no_ VG. It will be added by doing "drbdmanage add-node --external <nodeName> [IPaddress]". Is that correct? Thanks, Robert Riches