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Commit 565c1bb8 authored by David Hrbáč's avatar David Hrbáč
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Clean two spaces within text

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4 merge requests!368Update prace.md to document the change from qprace to qprod as the default...,!367Update prace.md to document the change from qprace to qprod as the default...,!366Update prace.md to document the change from qprace to qprod as the default...,!323extended-acls-storage-section
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...@@ -19,15 +19,15 @@ Anselm computer provides two main shared filesystems, the [HOME filesystem](#hom ...@@ -19,15 +19,15 @@ Anselm computer provides two main shared filesystems, the [HOME filesystem](#hom
A user file on the Lustre filesystem can be divided into multiple chunks (stripes) and stored across a subset of the object storage targets (OSTs) (disks). The stripes are distributed among the OSTs in a round-robin fashion to ensure load balancing. A user file on the Lustre filesystem can be divided into multiple chunks (stripes) and stored across a subset of the object storage targets (OSTs) (disks). The stripes are distributed among the OSTs in a round-robin fashion to ensure load balancing.
When a client (a compute node from your job) needs to create or access a file, the client queries the metadata server ( MDS) and the metadata target ( MDT) for the layout and location of the [file's stripes](http://www.nas.nasa.gov/hecc/support/kb/Lustre_Basics_224.html#striping). Once the file is opened and the client obtains the striping information, the MDS is no longer involved in the file I/O process. The client interacts directly with the object storage servers (OSSes) and OSTs to perform I/O operations such as locking, disk allocation, storage, and retrieval. When a client (a compute node from your job) needs to create or access a file, the client queries the metadata server ( MDS) and the metadata target ( MDT) for the layout and location of the [file's stripes](http://www.nas.nasa.gov/hecc/support/kb/Lustre_Basics_224.html#striping). Once the file is opened and the client obtains the striping information, the MDS is no longer involved in the file I/O process. The client interacts directly with the object storage servers (OSSes) and OSTs to perform I/O operations such as locking, disk allocation, storage, and retrieval.
If multiple clients try to read and write the same part of a file at the same time, the Lustre distributed lock manager enforces coherency so that all clients see consistent results. If multiple clients try to read and write the same part of a file at the same time, the Lustre distributed lock manager enforces coherency so that all clients see consistent results.
There is default stripe configuration for Anselm Lustre filesystems. However, users can set the following stripe parameters for their own directories or files to get optimum I/O performance: There is default stripe configuration for Anselm Lustre filesystems. However, users can set the following stripe parameters for their own directories or files to get optimum I/O performance:
1. stripe_size: the size of the chunk in bytes; specify with k, m, or g to use units of KB, MB, or GB, respectively; the size must be an even multiple of 65,536 bytes; default is 1MB for all Anselm Lustre filesystems 1. stripe_size: the size of the chunk in bytes; specify with k, m, or g to use units of KB, MB, or GB, respectively; the size must be an even multiple of 65,536 bytes; default is 1MB for all Anselm Lustre filesystems
2. stripe_count the number of OSTs to stripe across; default is 1 for Anselm Lustre filesystems one can specify -1 to use all OSTs in the filesystem. 2. stripe_count the number of OSTs to stripe across; default is 1 for Anselm Lustre filesystems one can specify -1 to use all OSTs in the filesystem.
3. stripe_offset The index of the OST where the first stripe is to be placed; default is -1 which results in random selection; using a non-default value is NOT recommended. 3. stripe_offset The index of the OST where the first stripe is to be placed; default is -1 which results in random selection; using a non-default value is NOT recommended.
!!! Note "Note" !!! Note "Note"
Setting stripe size and stripe count correctly for your needs may significantly impact the I/O performance you experience. Setting stripe size and stripe count correctly for your needs may significantly impact the I/O performance you experience.
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