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

[Jan-Frode Myklebust]

It’s a multiple of full blocks.



 -jf

tir. 21. mai 2019 kl. 20:06 skrev Todd Ruston <truston at mbari.org>:

> Hi Indulis,
>
> Yes, thanks for the reminder. I'd come across that, and our system is
> currently set to a stub size of zero (the default, I presume). I'd intended
> to ask in my original query whether anyone had experimented and found an
> optimal value that prevents most common inadvertent recalls by Macs. I know
> that will likely vary by file type, but since we have a broad mix of file
> types I figure a value that covers the majority of cases without being
> excessively large is the best we could implement.
>
> Our system is using 16MiB blocks, with 1024 subblocks. Is stub size
> bounded by full blocks, or subblocks? In other words, would we need to set
> the stub value to increments of 16MiB, or 16KiB?
>
> Cheers,
>
> - Todd
>
>
> On May 21, 2019, at 2:34 AM, Indulis Bernsteins1 <INDULISB at uk.ibm.com>
> wrote:
>
> 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 <INDULISB at UK.IBM.COM>*
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