[lustre-discuss] DNE2 settings are not propagated?
keith.mannthey at intel.com
Fri Mar 20 13:57:43 PDT 2020
Thanks Andreas and Cory very helpful. -D will help for what I am using it for.
From: Spitz, Cory James <cory.spitz at hpe.com>
Sent: Friday, March 20, 2020 12:57 PM
To: Andreas Dilger <adilger at whamcloud.com>; Mannthey, Keith <keith.mannthey at intel.com>
Cc: lustre-discuss at lists.lustre.org; Koutoupis, Petros <petros.koutoupis at hpe.com>
Subject: Re: [lustre-discuss] DNE2 settings are not propagated?
As Andreas says, it isn’t really recommended, but you can get sub-directories to inherit the striping by using the -D, --default option to `lfs mkdir` or `lfs setdirstripe`. From the man page:
Set the default striping pattern of subdirectories. Newly cre-
ated sub-directories will use the new default striping pattern,
but existing sub-directories will not be affected. The newly
created sub-directories will also inherit the specified default
striping pattern. Only default stripe count is supported for
Note that striping all directories across all MDTs by default is
not recommended at this time, as the clients will have to do
more RPCs to create and access each directory, hurting perfor-
mance rather than improving it. Default striped directories are
preferred for cases where large subdirectories will be created
(e.g. file-per-process job output directories).
On 3/20/20, 2:33 PM, "lustre-discuss on behalf of Andreas Dilger" <lustre-discuss-bounces at lists.lustre.org<mailto:lustre-discuss-bounces at lists.lustre.org> on behalf of adilger at whamcloud.com<mailto:adilger at whamcloud.com>> wrote:
On Mar 20, 2020, at 13:02, Mannthey, Keith <keith.mannthey at intel.com<mailto:keith.mannthey at intel.com>> wrote:
I am doing some work with Lustre 2.13 (Downloaded from Whamcloud) and DNE 2 there are 6 MDTs.
[root at colts52-clx01 for-test]# lfs getdirstripe TEST
lmv_stripe_count: 6 lmv_stripe_offset: 1 lmv_hash_type: fnv_1a_64
[root at colts52-clx01 for-test]# mkdir TEST/now
[root at colts52-clx01 for-test]# lfs getdirstripe TEST/now/
lmv_stripe_count: 0 lmv_stripe_offset: 2 lmv_hash_type: none
Directory stripping settings are not being propagated. Is this expected?
Yes, this working as designed. It isn't necessarily good for all directories to be striped, as that adds overhead without necessary improving performance.
The current recommendation is that DNE should be used for e.g. a top-level directory to distribute files and subdirectories across MDTs, or in the case of large directories with millions of files.
Principal Lustre Architect
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