On Fri, Nov 07, 2008 at 02:55:06PM -0500, Martin K. Petersen wrote: > > The current UNMAP proposal in SCSI doesn't have requirements either. > > Array vendors, suddenly realizing all the work they have to do to > support this, are now talking about imposing additional constraints > (orthogonal to the UNMAP command set) because of limitations in their > existing firmware architectures. Let's be just a *little* bit fair here. Suppose we wanted to implement thin-provisioned disks using devicemapper and LVM; consider that LVM uses a default PE size of 4M for some very good reasons. Asking filesystems to be a little smarter about allocation policies so that we allocate in existing 4M chunks before going onto the next, and asking the block layer to pool trim requests to 4M chunks is not totally unreasonable. Array vendors use chunk sizes > than typical filesystem chunk sizes for the same reason that LVM does. So to say that this is due to purely a "broken firmware architecture" is a little unfair. Regards, - Ted -- 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
