On Mon, May 29, 2006 at 04:19:55PM +0530, Srinivas, Vidya wrote: > Hi, Hi Vidya. > > I am checking dmraid functionality for RAID5 with 3 disks. I am using > the latest available patch on > http://people.redhat.com/heinzm/sw/dm/dm-raid45/ > I have some confusion in the same. > > The target length in the function raid_ctr in dm-raid4-5.c is being > displayed to me as the smallest disk sectors. No. > However, I understand that > the target length should be the total sectors (of all available disks) > available for data (which in my case should be 2 disk sectors since 1 > disk sectors would be utilized for parity) Yes, it's 'number of disks - 1' with a minimum of 3 disks. > > What I understand is, in the user level dmraid, in > lib/activate/activate.c, under dm_raid45, sectors value is calculated > by: > > Sectors = _smallest(lc,rs,0) > > And, the same sectors value is passed to _dm_raid45_bol. > > Whatever goes from this _dm_raid45_bol directly goes to the kernel > dm-raid4-5.c and under raid_ctr gets printed as ti->len right? So, the > smallest sectors (of all the devices) goes to ti->len. In my case also, > the smallest disk sectors is being printed as ti->len and not the total > data sectors. Am I wrong? If so, it would be wrong. The _smallest() calculation identifies the smallest of the deveices in a RAID set in order to make up sane mappings (i.e. all disks mapped to in a target line must have this minumum size). > > > Also, I had another doubt in dm-raid4-5.c, under static struct raid_type > raid_types[], values for raid5_ls is: > > {Raid5_ls. "RAID5 (left symmetric), 1, 3, raid5, left_sym}, where the > number of parity devices (being the 3rd parameter) is taken as 1. Well, that number indicates the capacity being used for parity chunks (i.e. 1 device). > > But, I feel, since there isn't any dedicated parity device for RAID5, > shouldn't this be taken as 0. When I take this as 1, I am getting the > error, target length not divisable by number of devices. Can you send me your metadata (files created by 'dmraid -rD', tar'ed/bzip2'ed into Srinivas_Vidya-raid5.tar.bz2), please. > > When I take it as 0, my RAID volume is being created and things seem to > work. Strange. Will lokk into this once I got your metadata. > > Any suggestions would be helpful > > Thanks > Vidya > > -- > > dm-devel@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/dm-devel -- Regards, Heinz -- The LVM Guy -- *** Software bugs are stupid. Nevertheless it needs not so stupid people to solve them *** =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Heinz Mauelshagen Red Hat GmbH Consulting Development Engineer Am Sonnenhang 11 Storage Development 56242 Marienrachdorf Germany Mauelshagen@xxxxxxxxxx PHONE +49 171 7803392 FAX +49 2626 924446 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- -- dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
