On Thursday 11 March 2010 18:34:56 Theodore Tso wrote: > On Mar 10, 2010, at 11:19 AM, Damian Lukowski wrote: > > I have practically no knowledge of Linux' block device drivers, > > but is this really a partitioning issue? I think the problem is > > with the filesystems when clustering multiple blocks without > > knowledge of the sector alignment and sector size of the underlying > > block device. Maybe it is a better solution to adapt the filesystem > > buffer routine which reads/writes data from/to the block device? > > No, it's really a partitioning issue. If the paging subsystem wants a 4k > block to fill a particular page, we need to read that 4k block into > memory. If we need to swap out that 4k block, we need to write that 4k > block to swap space, or to the memory segment's backing store. If the > partition is misaligned by 512 bytes, this is simply not possible. The > file system has to do what is requested of it by its users, and the > reality is that we need to do 4k aligned reads and writes with respect to > the beginning of the partition, far more often than not. > > Hence, if we want the best performance on 4k sector drives, the partition > needs to be aligned with respect to what is most desirable for the device > in question. > I guess, what he meant was, to keep filesystem blocks aligned, even if the partition is not. Say if the partition is mis-aligned by 512-bytes, let the filesystem waste 4k-512bytes and keep it's blocks aligned. But it might be a case of over-engineering, possibly requiring disk format change. Thanks Nikanth -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
