Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Thu, Dec 13, 2007 at 02:00:05PM +0100, Mark Hunting wrote: > 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. man fsync man fdatasync man sync wikipedia page_cache -- : Lars Ellenberg http://www.linbit.com : : DRBD/HA support and consulting sales at linbit.com : : LINBIT Information Technologies GmbH Tel +43-1-8178292-0 : : Vivenotgasse 48, A-1120 Vienna/Europe Fax +43-1-8178292-82 : __ please use the "List-Reply" function of your email client.