[gpfsug-discuss] [EXTERNAL] Intro, and Spectrum Archive self-service recall interface question

Indulis Bernsteins1 INDULISB at uk.ibm.com
Tue May 21 10:34:42 BST 2019


Have you tried looking at Spectrum Archive setting instead of Spectrum 
Scale?

You can set both the size of the "stub file" that remains behind when a 
file is migrated, and also the amount of data which would need to be read 
before a recall is triggered. This might catch enough of your recall 
storms... or at least help!

IBM Spectrum Archive Enterprise Edition V1.3.0: Installation and 
Configuration Guide
http://www.redbooks.ibm.com/abstracts/sg248333.html?Open

7.14.3 Read Starts Recalls: Early trigger for recalling a migrated file
IBM Spectrum Archive EE can define a stub size for migrated files so that 
the stub size initial
bytes of a migrated file are kept on disk while the entire file is 
migrated to tape. The migrated
file bytes that are kept on the disk are called the stub. Reading from the 
stub does not trigger
a recall of the rest of the file. After the file is read beyond the stub, 
the recall is triggered. The
recall might take a long time while the entire file is read from tape 
because a tape mount
might be required, and it takes time to position the tape before data can 
be recalled from tape.
When Read Start Recalls (RSR) is enabled for a file, the first read from 
the stub file triggers a
recall of the complete file in the background (asynchronous). Reads from 
the stubs are still
possible while the rest of the file is being recalled. After the rest of 
the file is recalled to disks,
reads from any file part are possible.
With the Preview Size (PS) value, a preview size can be set to define the 
initial file part size
for which any reads from the resident file part does not trigger a recall. 
Typically, the PS value
is large enough to see whether a recall of the rest of the file is 
required without triggering a
recall for reading from every stub. This process is important to prevent 
unintended massive
recalls. The PS value can be set only smaller than or equal to the stub 
size.
This feature is useful, for example, when playing migrated video files. 
While the initial stub
size part of a video file is played, the rest of the video file can be 
recalled to prevent a pause
when it plays beyond the stub size. You must set the stub size and preview 
size to be large
enough to buffer the time that is required to recall the file from tape 
without triggering recall
storms.
Use the following dsmmigfs command options to set both the stub size and 
preview size of
the file system being managed by IBM Spectrum Archive EE:
dsmmigfs Update -STUBsize
dsmmigfs Update -PREViewsize
The value for the STUBsize is a multiple of the IBM Spectrum Scale file 
system’s block size.
this value can be obtained by running the mmlsfs <filesystem>. The 
PREViewsize parameter
must be equal to or less than the STUBsize value. Both parameters take a 
positive integer in
bytes.


 
Regards,
 
Indulis Bernsteins
Systems Architect
IBM New Generation Storage


Phone: +44 792 008 6548
E-mail: INDULISB at UK.IBM.COM


Jackson House, Sibson Rd
Sale, Cheshire M33 7RR
United Kingdom




 
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
741598. 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU

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