[Lustre-discuss] Questions about Lustre ACLs

[Kilian CAVALOTTI]

Hi all,

I've got a couple questions about ACLs in Lustre:


1. When they're enabled on the MDS, can a client mount the filesystem 
without them? It doesn't seem to be the case, but at the same time, the 
mount.lustre manpage mentions the noacl option in the "client-specific" 
section.

See, for instance:

Checking ACLs on the MDS:
# lctl get_param -n mdc.home-MDT0000-mdc-*.connect_flags | grep acl
acl

Mounting the client with no ACLs
# mount -t lustre -o noacl ibmds2 at o2ib:/home /home

ACLs are still in use:
# strace ls -al /home/kilian/mpihw.c 2>&1 | grep xattr
getxattr("/home/kilian/mpihw.c", "system.posix_acl_access"..., 0x0, 0) 
= -1 ENODATA (No data available)
getxattr("/home/kilian/mpihw.c", "system.posix_acl_default"..., 0x0, 0) 
= -1 ENODATA (No data available)

I believe getxattr() should return EOPNOTSUPP instead of ENODATA, if 
ACLs were disabled.


2. My second question is about the overhead induced by the ACLs. I 
didn't do any quantifying measurements, but having ACLs enabled seems 
to slower all MDS operations. A "ls" in a directory containing a lot of 
files "feels" way slower when ACLs are enabled on the MDS. Is that 
something to be expected? 


Thanks,
-- 
Kilian