[DRBD-user] DRBD - one half of Proxmox cluster miscommunicating

Felix Frank ff at mpexnet.de
Tue Jul 31 13:24:38 CEST 2012

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On 07/31/2012 01:10 PM, James Gibbon wrote:
> OK. The VM images for the cluster are stored in two Cisco NAS
> units. Both the physical servers are connected to these using
> iSCSI, through two Cisco gigabit switches. So for example a 
> particular VM disk image might be visible, from both servers,
> as /dev/mapper/drbdvg0-vm--104--disk--1.

I see. Quite unusual I'd say, to have two drbd nodes that each use a
NAS as backing device. But it looks sound, judging from the config.
Thanks for that.

Out of curiosity: Do you gain *any* advantage from using NAS in this
setup instead of local disks in your drbd nodes?
I'd like to point out that the drbd latency cost per write in this setup
is probably (RTT between nodes) + (RTT between secondary and NAS), which
may be small overhead, but potentially sub-optimal nontheless.


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