Hi all, I am planning a cold standby database server pair with shared disks (over Fibre Channel). The database will use the devices without a filesystem, addressing block devices directly. I want to setup two external arrays, the devices should build a RAID 1 in pairs over both arrays. This is to handle failure of one complete array, which should not occur (because each array is itself redundant with double power, double controller). We need to do this to be able to replace one complete array without disturbing the database operation. The general plan is to make a md with raid 1 for each of the partitions. The cold standby machine should be able to take over the whole disk situation and the IP address which is used to access the database engine. This will be done via scripts, executed by heartbeat. I need to have a quick failover. OS is Debian Lenny, Machines are 2 Proc Opteron Quad core, Fibre Channel Adapters QLogic. Now my questions: Is it possible to setup the md devices on the cold standby machine already with one device missing (the fibre channel devices are visible by both machines at the same time) or will this action disturb the operation of the md raid on the active machine ? Or is it more safe to setup the devices when a failover takes place, because the md process checks the drive permanently ? If this setup is too dangerous, is it better to create the md initially with one device missing on failover or should I setup the device with two members (failover takes place on machine failure, so assuming the external arrays are not affected at this time, both should be accessible) ? I assume this would be faster than setting up the raid initially with two devices, because the raid 1 with one device missing does not have to check which device is more recent. The database could come up when the mds are created and then we would re-add the other devices, which triggers background processing, but the database is already working. Because the device was not missing very long, I assume the re-assign process would not take that long, correct ? Any thoughts on this ? Thanks, Marcus -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
