[Lustre-discuss] Backup of trusted extended attributes

[Hervé Kergourlay]

I would like to get informations about some specific lustre extended 
attributes backup and restore

When I create a file on my lustre FS, add acl and a test xattr named 
"attr1", with the standard tools "attr", there is 2 xattr

santos.root(55) [dev->Bin] attr -l /mnt/mycltlustre/hky/bck/file.txt
Attribute "lov" has a 56 byte value for /mnt/mycltlustre/hky/bck/file.txt
Attribute "attr1" has a 4 byte value for /mnt/mycltlustre/hky/bck/file.txt

with an own developped tools, there is I can see 2 lustre xattr, 
trusted.lov and lustre.lov

santos.root(56) [dev->Bin] tina_xattr -tst_num 1 -path_src 
/mnt/mycltlustre/hky/bck/file.txt
I "Vos:tst_stat"[3]Stat Posix "/mnt/mycltlustre/hky/bck/file.txt"
I "Vos:tst_stat"[9]
I "Vos:tst_stat"[9]xattr list size: 58
I "Vos:tst_stat"[9]
I "Vos:tst_stat"[9]xattr name[0] = trusted.lov
I "Vos:tst_stat"[11]  size: 56
I "Vos:tst_stat"[9]xattr name[1] = system.posix_acl_access
I "Vos:tst_stat"[11]  size: 44
I "Vos:tst_stat"[9]xattr name[2] = user.attr1
I "Vos:tst_stat"[11]  size: 4
I "Vos:tst_stat"[9]xattr name[3] = lustre.lov
I "Vos:tst_stat"[11]  size: 56


I see some informations on backup where extended attributes are supposed 
to be backuped and restored

https://bugzilla.lustre.org/show_bug.cgi?id=5716 or in the lustre - 
operation manual (chapter 15)

But I would like to get more informations about theses two extended 
attributes. Which role they have (store lustre splitting information, I 
could imagine), do we need really to backup them ? and restore them ?
They should be recreated as restoring a file, it's recreating a file ??

Or perhaps it's linked with the MDS backup, in case of full desaster / 
recovery.

my lustre config

santos.root(57) [dev->Bin] uname -a
Linux santos 2.6.18-128.7.1.el5_lustre.1.8.1.1 #1 SMP Tue Oct 6 05:48:57 
MDT 2009 x86_64 x86_64 x86_64 GNU/Linux

santos root(58) [dev->Bin] rpm -qa | grep lustre
lustre-modules-1.8.1.1-2.6.18_128.7.1.el5_lustre.1.8.1.1
lustre-1.8.1.1-2.6.18_128.7.1.el5_lustre.1.8.1.1
kernel-ib-1.4.2-2.6.18_128.7.1.el5_lustre.1.8.1.1
kernel-lustre-2.6.18-128.7.1.el5_lustre.1.8.1.1
lustre-ldiskfs-3.0.9-2.6.18_128.7.1.el5_lustre.1.8.1.1

Thanks
Hervé
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