[WIP] CA-192760: use noop scheduler for multipath devices #293
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We need to ensure we use noop IO scheduler for multipath devices and non local devices. We were used to do that in the storage manager but for devices going offline and added back this is not possible, becasue SM is not running all the time. This patch ensures the noop scheduler is set for specific devices and this setting is preserved even when SM is not running or when SM is not managing multipath (a potentially upcoming feature). Whit this rule, we use noop for any multipath device or any block device that is not on the ATA bus (a very weak decision rule to get an idea of locally attached devices). Signed-off-by: Germano Percossi <germano.percossi@citrix.com>
A decorator for deprecated functions has been created. Deprecation is this case means replacing them with a no-op function and a warning message. Signed-off-by: Germano Percossi <germano.percossi@citrix.com>
CA-192760: use noop IO scheduler for specific device types We need to ensure that a noop scheduler is used for the following devices: - non rotational disks (e.g. SSDs) - multipath devices (we assume they have a clever controller if many paths exist) - remote arrays In the latter case we are not sure the chosen rule is always doing the right thing. We were used to do that in the storage manager but for devices going offline and added back this is not possible, because SM is not running all the time. This patch ensures the noop scheduler is set for specific devices and this setting is preserved even when SM is not running or when SM is not explicitly managing multipath (a potentially upcoming feature). Signed-off-by: Germano Percossi <germano.percossi@citrix.com>
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Patch not ready to be pushed.
The following is pending:
that a slave device is set with an elevator different than the multipath dm devices does not necessarily
mean the kernel is taking that elevator really into account