Re: swidth with mdadm and RAID6

Steve Cousins
2006-09-18T20:45:46Z

Hi again,

Still no luck with 2.8.11:

[root@juno xfsprogs-2.8.11]# cd mkfs

[root@juno mkfs]# ./mkfs.xfs -f /dev/md0
meta-data=/dev/md0 isize=256 agcount=32, agsize=30524160
blks
= sectsz=4096 attr=0
data = bsize=4096 blocks=976772992, imaxpct=25
= sunit=16 swidth=144 blks, unwritten=1
naming =version 2 bsize=4096
log =internal log bsize=4096 blocks=32768, version=2
= sectsz=4096 sunit=1 blks
realtime =none extsz=589824 blocks=0, rtextents=0

Since I have a spare in there do you think it is starting with md.nr_disks
= 11 and then subtracting two?

Thanks,

Steve
______________________________________________________________________
Steve Cousins, Ocean Modeling Group Email: cousins@umit.maine.edu
Marine Sciences, 452 Aubert Hall http://rocky.umeoce.maine.edu
Univ. of Maine, Orono, ME 04469 Phone: (207) 581-4302

On Mon, 18 Sep 2006, Shailendra Tripathi wrote:

> Hi Steve,
> Both of us are using old xfsprogs. It is handled in new
> xfsprogs.
>
> */
> switch (md.level) {
> case 6:
> md.nr_disks--;
> /* fallthrough */
> case 5:
> case 4:
> md.nr_disks--;
> /* fallthrough */
> case 1:
> case 0:
> case 10:
> break;
> default:
> return 0;
>
>
> Regards,
>
> Shailendra Tripathi wrote:
>
> >> Hi Steve,
> >> I checked the code and it appears that XFS is not *aware*
> >> of RAID6. Basically, for all md devices, it gets the volume info by
> >> making a an ioctl call. I can see that XFS only take care of level 4
> >> and level 5. It does not account for level 6.
> >> Only extra line need to be added here as below:
> >>
> >> if (md.level == 6)
> >> md.nr_disks -= 2; /* RAID 6 has 2 parity disks */
> >> You can try with this change if you can. Do let mew know if it solves
> >> your problem.
> >>
> >> This code is in function: md_get_subvol_stripe in <xf_progs>/libdisk/md.c
> >>
> >>
> >> /* Deduct a disk from stripe width on RAID4/5 */
> >> if (md.level == 4 || md.level == 5)
> >> md.nr_disks--;
> >>
> >> /* Update sizes */
> >> *sunit = md.chunk_size >> 9;
> >> *swidth = *sunit * md.nr_disks;
> >>
> >> return 1;
> >> }
> >>
> >> Regards,
> >> Shailendra
> >> Steve Cousins wrote:
> >>
> >>> Hi Shailendra,
> >>>
> >>> Here is the info:
> >>>
> >>> 1. [root@juno ~]# cat /proc/mdstat Personalities : [raid6] md0 :
> >>> active raid6 sdb[0] sdl[10](S) sdk[9] sdj[8] sdi[7] sdh[6] sdg[5]
> >>> sdf[4] sde[3] sdd[2] sdc[1]
> >>> 3907091968 blocks level 6, 64k chunk, algorithm 2 [10/10]
> >>> [UUUUUUUUUU]
> >>> unused devices: <none>
> >>>
> >>> 2. mdadm --create /dev/md0 --chunk=64 --level=6 --raid-devices=10
> >>> --spare-devices=1 /dev/sd[bcdefghijkl]
> >>>
> >>> 3. [root@juno ~]# xfs_db -r /dev/md*
> >>> xfs_db> sb
> >>> xfs_db> p
> >>> magicnum = 0x58465342
> >>> blocksize = 4096
> >>> dblocks = 976772992
> >>> rblocks = 0
> >>> rextents = 0
> >>> uuid = 04b32cce-ed38-496f-811f-2ccd51450bf4
> >>> logstart = 536870919
> >>> rootino = 256
> >>> rbmino = 257
> >>> rsumino = 258
> >>> rextsize = 144
> >>> agblocks = 30524160
> >>> agcount = 32
> >>> rbmblocks = 0
> >>> logblocks = 32768
> >>> versionnum = 0x3d84
> >>> sectsize = 4096
> >>> inodesize = 256
> >>> inopblock = 16
> >>> fname = "\000\000\000\000\000\000\000\000\000\000\000\000"
> >>> blocklog = 12
> >>> sectlog = 12
> >>> inodelog = 8
> >>> inopblog = 4
> >>> agblklog = 25
> >>> rextslog = 0
> >>> inprogress = 0
> >>> imax_pct = 25
> >>> icount = 36864
> >>> ifree = 362
> >>> fdblocks = 669630878
> >>> frextents = 0
> >>> uquotino = 0
> >>> gquotino = 0
> >>> qflags = 0
> >>> flags = 0
> >>> shared_vn = 0
> >>> inoalignmt = 2
> >>> unit = 16
> >>> width = 144
> >>> dirblklog = 0
> >>> logsectlog = 12
> >>> logsectsize = 4096
> >>> logsunit = 4096
> >>> features2 = 0
> >>> xfs_db>
> >>>
> >>> Thanks for the help.
> >>>
> >>> Steve
> >>>
> >>> ______________________________________________________________________
> >>> Steve Cousins, Ocean Modeling Group Email: cousins@umit.maine.edu
> >>> Marine Sciences, 452 Aubert Hall http://rocky.umeoce.maine.edu
> >>> Univ. of Maine, Orono, ME 04469 Phone: (207) 581-4302
> >>>
> >>> On Mon, 18 Sep 2006, Shailendra Tripathi wrote:
> >>>
> >>>
> >>>
> >>>> Can you list the output of
> >>>> 1. cat /proc/mdstat
> >>>> 2. the command to create 8+2 RAID6 with one spare ?
> >>>> 3. and output of following:
> >>>> xfs_db -r /dev/md*
> >>>> xfs_db> sb
> >>>> xfs_db> p
> >>>>
> >>>> -shailendra
> >>>>
> >>>> Steve Cousins wrote:
> >>>>
> >>>>
> >>>>>> I have a RAID6 array of 11 500 GB drives using mdadm. There is one
> >>>>>> hot-spare so the number of data drives is 8. I used mkfs.xfs with
> >>>>>> defaults to create the file system and it seemed to pick up the
> >>>>>> chunk size
> >>>>>> I used correctly (64K) but I think it got the swidth wrong. Here
> >>>>>> is what
> >>>>>> xfs_info says:
> >>>>>>
> >>>>>> ===========================================================================
> >>>>>>
> >>>>>> meta-data=/dev/md0 isize=256 agcount=32,
> >>>>>> agsize=30524160
> >>>>>> blks
> >>>>>> = sectsz=4096 attr=0
> >>>>>> data = bsize=4096 blocks=976772992,
> >>>>>> imaxpct=25
> >>>>>> = sunit=16 swidth=144 blks,
> >>>>>> unwritten=1
> >>>>>> naming =version 2 bsize=4096
> >>>>>> log =internal bsize=4096 blocks=32768, version=2
> >>>>>> = sectsz=4096 sunit=1 blks
> >>>>>> realtime =none extsz=589824 blocks=0, rtextents=0
> >>>>>> ===========================================================================
> >>>>>>
> >>>>>>
> >>>>>> So, sunit*bsize=64K, but swidth=144 and swidth/sunit=9 so it looks
> >>>>>> like it
> >>>>>> thought there were 9 data drives instead of 8.
> >>>>>> Am I diagnosing this correctly? Should I recreate the array and
> >>>>>> explicitly set sunit=16 and swidth=128?
> >>>>>>
> >>>>>> Thanks for your help.
> >>>>>>
> >>>>>> Steve
> >>>>>> ______________________________________________________________________
> >>>>>>
> >>>>>> Steve Cousins, Ocean Modeling Group Email: cousins@umit.maine.edu
> >>>>>> Marine Sciences, 452 Aubert Hall http://rocky.umeoce.maine.edu
> >>>>>> Univ. of Maine, Orono, ME 04469 Phone: (207) 581-4302
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>
> >>>
> >>>
> >>
> >>
> >
> >
>