On 03/21/2016 02:24 AM, Bart Van Assche wrote: > On 03/19/16 08:18, Hannes Reinecke wrote: >> On 03/18/2016 10:56 PM, Bart Van Assche wrote: >>> On 03/17/2016 12:39 AM, Hannes Reinecke wrote: >>>> On larger installations it is useful to disable automatic LUN >>>> scanning, and only add the required LUNs via udev rules. >>>> This can speed up bootup dramatically. >>>> >>>> This patch introduces a new scan module parameter value 'manual', >>>> which works like 'none', but can be overriden by setting the >>>> 'rescan' >>>> value from scsi_scan_target to 'SCSI_SCAN_MANUAL'. >>>> And it updates all relevant callers to set the 'rescan' value >>>> to 'SCSI_SCAN_MANUAL' if invoked via the 'scan' option in sysfs. >>> >>> Hello Hannes, >>> >>> Will setting scsi_scan_type to 'manual' allow a system to boot >>> from a >>> SCSI disk? If not, are there alternatives to this approach? Would >>> it be >>> a valid alternative to e.g. introduce a new threshold parameter such >>> that only LUN numbers below this threshold are scanned during boot? >>> >> I have a patch for dracut, which will generate udev rules for all >> devices required for mounting the root fs. >> Once the system is booted properly I've got another patch for systemd >> which switches back to 'normal' scanning (ie by writing 'sync' into >> /sys/modules/scsi_mod/parameters/scan) and rescan all scsi hosts. >> >> With that there's no need to have any arbitrary limits; only the >> necessary devices are enabled during boot. > > Hello Hannes, > > That sounds like a really interesting approach. Will this approach > also work if the SCSI host and/or LUN numbers change during a reboot? > It's independent on the SCSI host as it just looks for the rport ID (FC WWPN, SAS ID, or iSCSI target name). The LUN number, however, is fixed; the whole point of this exercise is that you want to blank out individual LUNs behind a given target. Hence you need to able to address the LUNs in the first place. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@xxxxxxx +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
