Neil Brown wrote: > On Thursday April 12, rich@xxxxxxxxxxxxxx wrote: > >> I forgot to ask something, sorry. With RAID0 and all the odd size drives >> I have I'd get a lot of left over unused space. Is there anyway to make >> use of this slack? >> > > md/raid0 makes use of all available space (modulo chunk size). > To quote from "man md" > > RAID0 > A RAID0 array (which has zero redundancy) is also known as a striped > array. A RAID0 array is configured at creation with a Chunk Size which > must be a power of two, and at least 4 kibibytes. > > The RAID0 driver assigns the first chunk of the array to the first > device, the second chunk to the second device, and so on until all > drives have been assigned one chunk. This collection of chunks forms a > stripe. Further chunks are gathered into stripes in the same way which > are assigned to the remaining space in the drives. > > If devices in the array are not all the same size, then once the small‐ > est device has been exhausted, the RAID0 driver starts collecting > chunks into smaller stripes that only span the drives which still have > remaining space. That has to result in some bizarre transfer rate changes! I saved this explanation in my RAID stuff folder, clearly you could use techniques from raster graphics to make transfer rate more uniform, but since the most used will also be the fastest currently, that's probably not an optimization. -- bill davidsen <davidsen@xxxxxxx> CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - 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
