[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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