I am now looking at iSCSI. The problem is exactly what Matt describes. Recovery isn't that big of a deal, when the other server comes up I can carefully set one of the devices as failed, remove it, add it again, and get them to sync. after a sync is complete on both servers, I can mount the drive on the server that went down and resume services. Maybe iSCSI will report things diferently to md (raid). I will try. I'm looking forward to cmirror, I hear it will be ready soon. I'm not completely sure it's what I need, maybe someone involved will see this and chime in. -Derek On 7/27/05, Matthew Gillen <me@mattgillen.net> wrote: > AJ Lewis wrote: > > On Wed, Jul 27, 2005 at 09:06:01AM -0400, Matthew Gillen wrote: > > > >>Fury wrote: > >> > >>>I've racked my brain on this one, so hopefully someone will be of some help. > >>> > >>>I'm trying to set up two servers which share a drive and do not have a > >>>Single Point of Failure. They are on a local network with each other. > >>> The best solution would be to have /dev/sda1 on one server mirrored > >>>with /dev/sda1 on the second server. > >>>... > >>>A second solution was to use GFS/GNBD. I can export each drive to the > >>>other server, and do RAID 1 (on both servers) between the local > >>>/dev/sda1 and the remote gnbd device. I then format the raid device > >>>with GFS so both servers can mount it. > >>> > >>>Surprisingly, this last system works. Both systems can mount the > >>>drive and read-write to it. However, if either server in this > >>>configuration drops dead, the other server cannot deal with the dead > >>>gnbd device, and the raid device and mount point are no longer usable. > >>> I'm sure there are numerous other problems with this setup, also. > >>> > >>>So I'm looking for ideas. With two servers, how can I mirror a drive > >>>in real-time, and allow for failover? > >> > >>You might want to use something more like iSCSI + RAID: > >>http://linux-iscsi.sourceforge.net/ > > > > > > How is that different than GNBD + RAID? The issue isn't the network > > transport, it's recovery of a RAID on two nodes simultaneously. > I don't think he was even worried about recovery, although you're right > and that's another problem. I read that he couldn't access anything > after a failure of one server, which is what I was addressing. > > Honestly, I don't know how GNBD works. But if it makes makes the remote > volume look local and doesn't report problems in a way that RAID > understands (or at all), I can see how things would hang (just like a > client system would hang if an NFS server for a mounted filesystem went > down). I imagine (but I don't know from personal experience) that iSCSI > (with the ConnFailTimeout=x sec) would report a failed write and RAID > knows how to handle that. > > But, like I said, I don't know for sure about any of this, since I > haven't tried it. However, the page: > http://linas.org/linux/raid.html > mentions iSCSI, so it appears that some people have gotten it to work. > --Matt > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ > _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
