Highly available iSCSI target

Question

I'm in the process of setting up iSCSI target on DRBD following the steps detailed here.

I would appreciate if someone can answer and explain the following queries:

1. Is there a way to set up just 1 resource for iscsi config and storage? Why does iscsi.config have to have a separate resource (in drbd.conf).

2. Is it possible to put iscsi.config and iscsi.target in one disk?

3. If not possible, what would be a good ratio (space wise) for iscsi.config and iscsi.target? Assuming I need to set up a 1TB iscsi.storage, how much space should I allocate for iscsi.config?

Answer 1

What you do it establish a small filesystem and replicate it using DRBD; then make sure this filesystem is the first one to be enabled by the DRBD primary using Heartbeat, Pacemaker or similar product. In this file-system you keep the configuration file directories that will be shared across both servers. I do this for Samba and iSCSI.

/etc/samba --> /mnt/configfs/samba

/etc/iet --> /mnt/configfs/iet

On the primary server, mount the filesystem and then establish the symlinks. I will typically preserve the base directories (mv /etc/samba /etc/samba.original) before I establish symlinks. Once complete and everything is working you need to transfer DRBD primary to your secondary server, mount the shared file-system and establish the symlinks on that server.

At this point you should be able to enable your HA services on the DRBD primary and subsequently add any additional filesystems as you build-up the server capabilities.