<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi Indulis,<div class=""><br class=""></div><div class="">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.</div><div class=""><br class=""></div><div class="">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?</div><div class=""><br class=""></div><div class=""><div class="">Cheers,</div><div class=""><br class=""></div><div class="">- Todd</div><div class=""><br class=""></div><div><br class=""><blockquote type="cite" class=""><div class="">On May 21, 2019, at 2:34 AM, Indulis Bernsteins1 <<a href="mailto:INDULISB@uk.ibm.com" class="">INDULISB@uk.ibm.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style=" font-size:10pt;font-family:Helvetica" class="">Have you tried looking

at Spectrum Archive setting instead of Spectrum Scale?</span>

<br class="">

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">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!</span>

<br class="">

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class=""><b class=""><u class="">IBM Spectrum

Archive Enterprise Edition V1.3.0: Installation and Configuration Guide</u></b></span>

<br class=""><a href="http://www.redbooks.ibm.com/abstracts/sg248333.html?Open" class=""><span style=" font-size:10pt;color:blue;font-family:Helvetica" class="">http://www.redbooks.ibm.com/abstracts/sg248333.html?Open</span></a>

<br class="">

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class=""><i class="">7.14.3 Read

Starts Recalls: Early trigger for recalling a migrated file</i></span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">IBM Spectrum Archive

EE can define a stub size for migrated files so that the stub size initial</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">bytes of a migrated

file are kept on disk while the entire file is migrated to tape. The migrated</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">file bytes that

are kept on the disk are called the <span style=" font-size:11pt;font-family:TimesNewRoman,Italic" class=""><i class="">stub<span style=" font-size:10pt;font-family:Helvetica" class="">.

Reading from the stub does not trigger</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">a recall of the

rest of the file. After the file is read beyond the stub, the recall is

triggered. The</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">recall might take

a long time while the entire file is read from tape because a tape mount</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">might be required,

and it takes time to position the tape before data can be recalled from

tape.</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">When Read Start

Recalls (RSR) is enabled for a file, the first read from the stub file

triggers a</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">recall of the complete

file in the background (asynchronous). Reads from the stubs are still</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">possible while

the rest of the file is being recalled. After the rest of the file is recalled

to disks,</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">reads from any

file part are possible.</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">With the Preview

Size (PS) value, a preview size can be set to define the initial file part

size</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">for which any reads

from the resident file part does not trigger a recall. Typically, the PS

value</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">is large enough

to see whether a recall of the rest of the file is required without triggering

a</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">recall for reading

from every stub. This process is important to prevent unintended massive</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">recalls. The PS

value can be set only smaller than or equal to the stub size.</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">This feature is

useful, for example, when playing migrated video files. While the initial

stub</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">size part of a

video file is played, the rest of the video file can be recalled to prevent

a pause</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">when it plays beyond

the stub size. You must set the stub size and preview size to be large</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">enough to buffer

the time that is required to recall the file from tape without triggering

recall</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">storms.</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">Use the following

</span><span style=" font-size:10pt;font-family:Helvetica-Bold" class=""><b class="">dsmmigfs

</b></span><span style=" font-size:10pt;font-family:Helvetica" class="">command

options to set both the stub size and preview size of</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">the file system

being managed by IBM Spectrum Archive EE:</span>

<br class=""><span style=" font-size:10pt;font-family:BookMasterGothic-Bold" class=""><b class="">dsmmigfs

Update -STUBsize</b></span>

<br class=""><span style=" font-size:10pt;font-family:BookMasterGothic-Bold" class=""><b class="">dsmmigfs

Update -PREViewsize</b></span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">The value for the

</span><span style=" font-size:10pt;font-family:BookMasterGothic-Bold" class=""><b class="">STUBsize

</b></span><span style=" font-size:10pt;font-family:Helvetica" class="">is a multiple

of the IBM Spectrum Scale file system’s block size.</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">this value can

be obtained by running the </span><span style=" font-size:10pt;font-family:BookMasterGothic-Bold" class=""><b class="">mmlsfs

<filesystem><span style=" font-size:10pt;font-family:Helvetica" class="">.

The </span><span style=" font-size:10pt;font-family:BookMasterGothic-Bold" class=""><b class="">PREViewsize

</b></span><span style=" font-size:10pt;font-family:Helvetica" class="">parameter</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">must be equal to

or less than the </span><span style=" font-size:10pt;font-family:BookMasterGothic-Bold" class=""><b class="">STUBsize

</b></span><span style=" font-size:10pt;font-family:Helvetica" class="">value. Both

parameters take a positive integer in</span>

<br class=""><span style=" font-size:10pt;font-family:Helvetica" class="">bytes.</span><span style=" font-size:10pt;font-family:sans-serif" class=""><br class="">

</span>

<br class=""><div style="margin-bottom: 240px;" class=""><span style=" font-size:9pt;font-family:Arial" class=""> </span><span class="" style="font-size: 10pt; font-family: Arial;">Regards,</span></div><span style=" font-size:10pt;font-family:Arial" class=""> </span>

<br class=""><span style=" font-size:14pt;color:#8f8f8f;font-family:Arial" class=""><b class="">Indulis

Bernsteins</b></span><span style=" font-size:10pt;font-family:Arial" class=""><br class="">

Systems Architect<br class="">

IBM New Generation Storage</span>

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