On Friday February 13, dan.j.williams@xxxxxxxxx wrote: > Subject: md: 'size_limit' attribute > From: Dan Williams <dan.j.williams@xxxxxxxxx> > > Provide a sysfs attribute to allow a raid array to be truncated to an > arbitrary size. This functionality is needed to support imsm raid > arrays where the metadata format expects that the size of some arrays is > rounded down to the nearest 1MB boundary. Well it's not April 1st, so I assume you are serious. It really truncates the array, not the individual drives? So you could have e.g. a raid0 in which only some of the last stripe was used? Can you give me a concrete example of an array where this will make a required difference? I just want to be sure I understand. I guess you couldn't just add an 'array_size' attribute which gave direct access to mddev->array_size because that gets set when the array is started, and we want to be able to impose the limit before starting the array.... How about a semantic where starting the array will only modify ->array_size if it's value is zero of if it would reduce the value. How might this interact with array resizing? You add a drive to an array, reshape it, and then it doesn't get any bigger until the size_limit is updated? I guess that could work but it might be confusing.... though presumably mdadm/mdmon would know to look after all the details. What would you think of renaming the attribute to 'array_size' with the semantic of "once user-space sets it, the kernel will never change it" ?? NeilBrown -- 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
