[lustre-discuss] default directory striping with Lustre 2.8

[Faaland, Olaf P.]

Hi,

Suppose you have m MDTs in your filesystem, and create a new directory and set default directory striping using

lfs mkdir --count=c --index=k <path> && lfs setdirstripe --default --count=c <path>

Suppose that c < m and m > 2.

Then you make subdirectories, like

mkdir <path>/child.{1,2,3,...}

a) By design, do the child directories have the same starting index as <path>?
b) By design, are the child directories all striped across the same set of MDTs as <path>?

I didn't see that specified one way or the other in the DNE phase 2 high level design document at http://wiki.opensfs.org/DNE_StripedDirectories_HighLevelDesign_wiki_version.    If I should look elsewhere, let me know.

In a test I was doing today, I noticed that neither (a) nor (b) were true in practice.  I'm wondering whether that's a bug or a feature.  Here's partial output from my test.

$ lfs mkdir --count=6 --index=2 /p/lustre/faaland1/count6_index2
$ lfs setdirstripe -D --count=6 /p/lustre/faaland1/count6_index2
$ mkdir /p/lustre/faaland1/count6_index2/subdir.{1,2,3,4,5,6,7,8,9,10,11,12,13,14}
$ lfs getdirstripe /p/lustre/faaland1/count6_index2
/p/lustre/faaland1/count6_index2
lmv_stripe_count: 6 lmv_stripe_offset: 2
mdtidx           FID[seq:oid:ver]
     2           [0x280000400:0x33f3:0x0]
     3           [0x2c0000404:0x33f3:0x0]
     4           [0x300000402:0x33f2:0x0]
     5           [0x340000407:0x33f1:0x0]
     6           [0x380000406:0x33f0:0x0]
     7           [0x3c0000404:0x33ef:0x0]
/p/lustre/faaland1/count6_index2/subdir.4
lmv_stripe_count: 6 lmv_stripe_offset: 2
mdtidx           FID[seq:oid:ver]
     2           [0x280000400:0x33f5:0x0]
     3           [0x2c0000404:0x33f5:0x0]
     4           [0x300000402:0x33f4:0x0]
     5           [0x340000407:0x33f3:0x0]
     6           [0x380000406:0x33f2:0x0]
     7           [0x3c0000404:0x33f1:0x0]
/p/lustre/faaland1/count6_index2/subdir.9
lmv_stripe_count: 6 lmv_stripe_offset: 5
mdtidx           FID[seq:oid:ver]
     5           [0x340000400:0x37a1:0x0]
     6           [0x380000405:0x37a1:0x0]
     7           [0x3c0000402:0x37a0:0x0]
     8           [0x40000040e:0x379f:0x0]
     9           [0x440000403:0x379e:0x0]
     0           [0x200000405:0x379d:0x0]
/p/lustre/faaland1/count6_index2/subdir.3
lmv_stripe_count: 6 lmv_stripe_offset: 5
mdtidx           FID[seq:oid:ver]
     5           [0x340000400:0x37a0:0x0]
     6           [0x380000405:0x37a0:0x0]
     7           [0x3c0000402:0x379f:0x0]
     8           [0x40000040e:0x379e:0x0]
     9           [0x440000403:0x379d:0x0]
     0           [0x200000405:0x379c:0x0]
/p/lustre/faaland1/count6_index2/subdir.14
lmv_stripe_count: 6 lmv_stripe_offset: 7
mdtidx           FID[seq:oid:ver]
     7           [0x3c0000400:0x30d4:0x0]
     8           [0x400000403:0x30d4:0x0]
     9           [0x440000405:0x30d3:0x0]
     0           [0x200000407:0x30d2:0x0]
     1           [0x240000407:0x30d1:0x0]
     2           [0x280000407:0x30d0:0x0]
...


Olaf P. Faaland
Livermore Computing
phone : 925-422-2263
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