[gpfsug-discuss] preventing HSM tape recall storms

Fri Jul 6 17:36:14 BST 2018

Thanks Christof,

we had left out "gpfs" from the

vfs objects =
line in smb.conf

so setting
vfs objects = gpfs (etc)
gpfs:hsm = yes
gpfs:recalls = yes  (not "no" as I had originally, and is implied by the manual)

and setting the offline flag on the file by migrating it, so that
# mmlsattr -L  filename.jpg
...
Misc attributes:      ARCHIVE OFFLINE

now Explorer on Windows 7 and 10 do not recall the file while viewing the folder with "Large icons"

and a standard icon with an X is displayed.

But after the file is then opened and recalled, the icon displays the thumbnail image and the OFFLINE flag is lost.

Also as you observed, Finder on  MacOSX 10.13 ignores the file's offline flag,

so we still risk a recall storm caused by them.

All the best,

Cameron

________________________________
From: gpfsug-discuss-bounces at spectrumscale.org <gpfsug-discuss-bounces at spectrumscale.org> on behalf of Christof Schmitt <christof.schmitt at us.ibm.com>
Sent: 03 July 2018 20:37:08
To: gpfsug-discuss at spectrumscale.org
Cc: gpfsug-discuss at spectrumscale.org
Subject: Re: [gpfsug-discuss] preventing HSM tape recall storms

> 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.

SMB clients can query file information, including the OFFLINE
flag. With Spectrum Scale and the "gpfs" module loaded in Samba that
is mapped from the the OFFLINE flag that is visible in "mmlsattr
-L". In those systems, the SMB client can determine that a file is
offline.

In our experience this is handled correctly in Windows Explorer; when
an "offline" file is encountered, no preview is generated from the
file data. The Finder on Mac clients does not seem to honor the
OFFLINE flag, thus the main problems are typically recall storms
caused by Mac clients.

> According to the Samba documentation this is preventable by setting the following
> ----------------------------------------------
> 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.
> --------------------------------------------------
>
> 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)

These options apply to the "gpfs" module in Samba. The Samba version
you are using needs to be built with GPFS support and the "gpfs"
module needs to be loaded through the "vfs objects" configuration. As
Centos7/Samba4.5 is mentioned, would guess that the CentOS provided
Samba version is used, which is probably not compiled with GPFS
support.

>From IBM we would recommend to use CES for protocol services, which
also provides Samba for SMB. The Samba provided through CES is
configured so that the gpfs:recalls option can be used:

https://www.ibm.com/support/knowledgecenter/en/STXKQY_4.2.3/com.ibm.spectrum.scale.v4r23.doc/bl1adm_mmsmb.htm

gpfs:recalls
    If the value is set as yes files that have been migrated from disk
    will be recalled on access. By default, this is enabled. If
    recalls = no files will not be recalled on access and the client
    will receive ACCESS_DENIED message.

> 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 ?

Yes, they are working, as we use them in our Samba build. Debugging
this would require looking at the Samba configuration and possibly
collecting a trace. If my above assumption was wrong and this problem
occurs with the CES Samba (gpfs.smb), please open a PMR for debugging
this issue. If this is not the CES Samba, please contact the provider
of the Samba package for additional support.

Regards,

Christof

Christof Schmitt || IBM || Spectrum Scale Development || Tucson, AZ
christof.schmitt at us.ibm.com  ||  +1-520-799-2469    (T/L: 321-2469)

----- Original message -----
From: Cameron Dunn <Cameron.Dunn at bristol.ac.uk>
Sent by: gpfsug-discuss-bounces at spectrumscale.org
To: "gpfsug-discuss at spectrumscale.org" <gpfsug-discuss at spectrumscale.org>
Cc:
Subject: [gpfsug-discuss] preventing HSM tape recall storms
Date: Tue, Jul 3, 2018 6:22 AM

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
----------------------------------------------
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.
--------------------------------------------------

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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