Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Tue, Dec 05, 2017 at 06:28:05PM +0000, Riches Jr, Robert M wrote: > (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? yes. Regards, rck