<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
On 02/06/2018 11:23 AM, E.S. Rosenberg wrote:<br>
<blockquote type="cite"
cite="mid:CA+K1OzRv75i0UjDURBAVFYt7Dr0zMM7Z4VH0LMwocCM4dbbU=A@mail.gmail.com">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<div dir="ltr">Hi Cameron,<br>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Mon, Feb 5, 2018 at 10:54 PM,
Cameron Harr <span dir="ltr"><<a
href="mailto:harr1@llnl.gov" target="_blank"
moz-do-not-send="true">harr1@llnl.gov</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Greetings,<br>
<br>
I'll be retiring a 2.5 ZFS-backed file system in the
coming months and plan on putting it in a "read-only"
state for 6 weeks or so to let users archive or migrate
data they want. The optimal, if slightly contradictory,
definition of "read-only" for me would be to allow
unlinks, but disallow all other writes; however, if that's
not possible, then disallowing all writes would be
sufficient. I will be doing some testing, but our 2.5
T&D system won't be available for several days and am
therefore soliciting advice up front.<br>
<br>
Option 1 is to remount the file system on the clients in
read-only mode, but I can imagine a couple problems with
this method.<br>
</blockquote>
<div>Just out of curiosity what type of problems do you
fore-see? Missing a client still being rw? <br>
</div>
</div>
</div>
</div>
</blockquote>
<br>
There are potentially thousands of clients for some of the systems
and I can foresee missing clients as well as having many clients
hang when remounting due to open files. It can also be tedious given
a large number of different systems. Regardless, I may very well
end up doing this client remount anyway. <br>
<blockquote type="cite"
cite="mid:CA+K1OzRv75i0UjDURBAVFYt7Dr0zMM7Z4VH0LMwocCM4dbbU=A@mail.gmail.com">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<br>
Option 2 is to deactivate the OSTs with lctl, but that
also leaves me with some questions. In section 14.8.3.1a
of the Lustre manual, it recommends setting
max_create_count=0 with Lustre 2.9 and above. I'm using
2.5, not 2.9, but noticed that
/proc/fs/lustre/osp/fs-*-osc-M<wbr>DT0000/max_create_count
does indeed exist. Does setting that option in 2.5 still
have an effect in prohibiting new file and directory
creates? Additionally, will clients be OK having all OSTs
inactive?<br>
</blockquote>
<div>There was some discussion of making a/multiple OSTs
read-only for data migration last year that you may find
useful:<br>
<a
href="http://lists.lustre.org/pipermail/lustre-discuss-lustre.org/2017-March/014294.html"
moz-do-not-send="true">http://lists.lustre.org/pipermail/lustre-discuss-lustre.org/2017-March/014294.html</a><br>
</div>
</div>
</div>
</div>
</blockquote>
<br>
Thanks Eli. I didn't know about the "degraded" option. I'll try
setting that on the OSTs and deactivating the OSTs on the MDS
(though it's not clear if unlinks are allowed back in 2.5 or just
2.9+).<br>
-Cameron<br>
<br>
</body>
</html>