[Lustre-discuss] more on MGS and MDT separation
Ms. Megan Larko
dobsonunit at gmail.com
Thu Oct 22 12:41:30 PDT 2009
Greetings,
I am deactivating an older Lustre filesystem in favor of a newer one
(already up and stable).
The message in Lustre-discuss Digest Vol 45 Issue 22 stated (with two
of my comments in-line):
Message: 2
Date: Sun, 11 Oct 2009 19:05:07 +0200
From: Bernd Schubert <bs_lists at aakef.fastmail.fm>
Subject: Re: [Lustre-discuss] Moving MGS to separate device
To: lustre-discuss at lists.lustre.org
Message-ID: <200910111905.08076.bs_lists at aakef.fastmail.fm>
Content-Type: Text/Plain; charset="iso-8859-15"
Hello Wojciech,
I already did this several times, here are the steps I so far used:
1) Remove MGS from MDT-device
tunefs.lustre --nogms /dec/mdt_device
^^^^
Megan: I am assuming "--nomgs" here.
2) Create new MGS
mkfs.lustre --mgs /dev/mgs_device
3) Make sure OSTs and MDTs re-register with the MGS:
tunefs.lustre --writeconf /dev/device
Megan: Do I need to do this even if the MGS is being moved
from a shared device with an MDT to its own device/hard drive on the
same physical server (same MAC addr, IP, hostname etc.....)?
I'm not sure if writeconf is really necessary, but so far I always did it to
make sure everything goes smoothly (clients shouldn't have the filesystem
mounted at this step).
5) Mount MGS, MDT, OSTs
4) Re-apply settings done with lctl.
Megan: Why are the above ordered the way they are? Shouldn't
I mount first and then apply the settings? (I didn't think I could
"lctl" an unmounted OST/MDT etc.)
As you also wrote (private mail), it might be possible to just copy over the
CONFIGS directory, but I never tried to do that.
Hope it helps,
Bernd
Megan: Thanks!
Additionally in Lustre-discuss Digest Vol 45 Issue 36 A. Dilger opined:
"...128Mb is the max size the MGS would ever need."
Wow! That is small. I know the MGS does not store the sort of data
retained on an MDT for a multi-Tb filesystem, but really 128Mb max
would be used?
Thanks for you advice!
Megan Larko
More information about the lustre-discuss
mailing list