Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi all, I have set up DRBD (0.7.21, Debian Etch) on two storage systems. Both systems use a Areca Raid controller with 1GB cache memory. When I copy a file to the DRBD device on the primary, the copying finishes with a speed of about 400MB per second. That's should be impossible, DRBD uses a gigabit link to synchronize, the copying should proceed with a rate op 100 MB per second (drbd.conf: rate 100M). So apparently the copying finishes before the data is transferred to the secondary. Indeed I still see a lot of DRBD network traffic for some seconds after the copy command finishes. This should be impossible with DRBD, the copying should only finish when the data is both written on the primary AND the secondary, right? When the primary server unexpectedly goes down right after a file has been copied and the secondary server takes over, the copied file is not there. I think this has to do with the 1GB cache memory on the Areca cards, when I transfer files that are much bigger than 1GB the copying indeed finishes with a speed close to 100MB per second. I don't understand this, what difference does it make for DRBD what is underneath the DRBD device (/dev/drbd0)? It should not matter if there is only one hard disk, a RAID system, a RAID system with cache memory or whatever. But apparently it does matter in my case. Is this a known problem, and how can I avoid it? Right now I can never be sure my two storage systems are fully synchronized. Thanks a lot Mark