Hi Luca, Okay, let's assume a chunk size of C. No matter what your md looks like, the logical md volume consists of a series of size/C chunks. the very first chunk C0 will hold the LVM header. If I align the extends with the chunksize and the extends even have the chunksize, then every extens PEx of my PV equals exactly a chunk on any of the disks. Which in turn means, if I want to read PEx I have to read some chunk Cy on one disk, and PEx+1 would most certainly be a Chunk Cy+1 which would reside on a different physical disk. So the question is: Why would you want to align the first PE to the stripesize, rather then the chunksize? Regards -Sven On Mon, April 20, 2009 07:39, Luca Berra wrote: > On Sun, Apr 19, 2009 at 05:16:21PM +0200, Sven Eschenberg wrote: >> Unfortunately I don't have the box at hand for 2 days, but I asked md to >> use a chunksize of 2048K and the /proc/mdstat reported 2048K, last time >> I >> checked. >> The LVM hat a phy-extsize of 2M and with the --dataalignment option set >> to >> 2M, pvs reported a pe_start value of 2M aswell. > > if you have a 2M chunk size, a full stripe is 2M*(N-1), where N-1 is the > number of drives in your array minus redundancy. (i.e. for a 5 drive > raid5 a stripe size would be 8M). > > L. > > -- > Luca Berra -- bluca@comedia.it > Communication Media & Services S.r.l. > /"\ > \ / ASCII RIBBON CAMPAIGN > X AGAINST HTML MAIL > / \ > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ > _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
