[gpfsug-discuss] preventing HSM tape recall storms

[Cameron Dunn]

HSM over LTFS-EE runs the risk of a recall storm if files which have been migrated to tape
are then shared by Samba to Macs and PCs.
MacOS Finder and Windows Explorer will want to display all the thumbnail images of a
folder's contents, which will recall lots of files from tape.

According to the Samba documentation this is preventable by setting the following
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https://www.samba.org/samba/docs/current/man-html/vfs_gpfs.8.html

gpfs:recalls = [ yes | no ]
When this option is set to no, an attempt to open an offline file
will be rejected with access denied.
This helps preventing recall storms triggered by careless applications like Finder and Explorer.

yes(default) - Open files that are offline. This will recall the files from HSM.
no - Reject access to offline files with access denied. This will prevent recalls of files from HSM.
Using this setting also requires gpfs:hsm to be set to yes.

gpfs:hsm = [ yes | no ]
Enable/Disable announcing if this FS has HSM enabled.
no(default) - Do not announce HSM.
yes - Announce HSM.
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However we could not get this to work.

On Centos7/Samba4.5, smb.conf contained
gpfs:hsm = yes
gpfs:recalls = no
(also tried setting gpfs:offline = yes, though this is not documented)

We made a share containing image files that were then migrated to tape by LTFS-EE,
to see if these flags were respected by OS X Finder or Windows Explorer.

Neither Mac OS X (using SMB3) or Windows 7 (using SMB2) respected the settings,
so that when browsing the stubs in the share, the files were recalled from tape
and the thumbnails displayed.

Has anyone seen these flags working as they are supposed to ?

Many thanks for any ideas,

Cameron


Cameron Dunn
Advanced Computing Systems Administrator
Advanced Computing Research Centre
University of Bristol
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