Hello, I'm facing a problem with Xen machines that depends on MD devices. As I'm new to systemd world, I might not be seeing the clean solution. That's why I'm asking for an advice.
MD devices are automatically detect by udev. If device state is safe, /dev/md/myraid is started. However, if the state is not safe (like a raid with a missing disk), udev starts [email protected] that tries to start the device anyway after 30s. As mdadm-last-resort conflicts with the device presence, it will not run if the required disk appears before 30s. Even with mdadm-last-resort running, MD device might still be usable, although degraded. Xen VM are started by xendomains.service, that simply calls a shell script like in SysV times. It start a bunch of VM in sequence. xendomains.service has only generic dependencies that let it run at a very early stage. Now the problem: If for any reason, a MD device takes some seconds to appear (or even 30s as the last resort), xendomains will fail to start any machine that depends on that MD device. I'm extending manually xendomains.service to depend on a series of MD devices, that fixed the start order problem. However, I created new problems. First I had to frequently regenerate those "Requires" as machines are frequently started/migrated between hosts (I also consider using systemd generators). But worse, whenever a single MD device permanently fails, xendomains is never started and all those VM that does not use the failed MD never start. I though that maybe I could use instances ([email protected]) to launch VM individually, each of them depending on those devices it uses. However, these instances would have to be dynamically generated based on its configuration (systemd generators from /etc/xen/vm/xxx.cfg?), either on boot, shutdown or simply periodically. The stop procedure will still be the same, calling the SysV script as systemd will not know about VM (re)started after boot. I even though about simply create an alternative xendomains.service that does not depend on any MD device and launch it using a systemd timer if the xendomains that depends on MD devices isn't started after 30s. It looks ugly but it might work. Regards, -- Luiz Angelo Daros de Luca [email protected]
_______________________________________________ systemd-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/systemd-devel
