> It seems to me that unmap is not all that different, why do we need to > do it even close in time proximity to the deletes? With a bitmap, we > have total timing control of when the unmaps are forwarded down to the > device. I like that timing control much better than a cache and > coalesce approach. The trouble I see with a bitmap is the amount of memory it consumes. It seems that discards must be tracked on no bigger than 4KB sectors (and possibly even 512 byte sectors). But even with 4KB, then, say, a 32 TB volume (just 16 * 2TB disks, or even lower end with thin provisioning) requires 1 GB of bitmap memory. Which is a lot just to store, let alone walk over etc. - R. -- 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
