It’s a multiple of full blocks.
-jf tir. 21. mai 2019 kl. 20:06 skrev Todd Ruston <[email protected]>: > 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 <[email protected]> > 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:* *[email protected] <[email protected]>* > [image: Description: Description: IBM] > > Jackson House, Sibson Rd > Sale, Cheshire M33 7RR > United Kingdom > <Mail Attachment.png><Mail Attachment.png><Mail Attachment.png><Mail > Attachment.png><Mail Attachment.png> > > > > 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 > _______________________________________________ > gpfsug-discuss mailing list > gpfsug-discuss at spectrumscale.org > http://gpfsug.org/mailman/listinfo/gpfsug-discuss > > > _______________________________________________ > gpfsug-discuss mailing list > gpfsug-discuss at spectrumscale.org > http://gpfsug.org/mailman/listinfo/gpfsug-discuss >
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