Hi Peter,
Can you please elaborate on how resizing an LVM will cause Lustre to
resize?
Yeah, I know you can have OST on top of an LVM-based logical-volumn. But
my understanding (from a previous mail in this alias) is OST can't
reflect the size change of the underlying logical volumn it is based on.
In plain words, if I do a lvextend or lvreduce on that logical-volumn,
Lustre won't pick the OST size change and hence it won't reflect in the
size change in the filesystem that OST is participating in. Is this
understanding correct?
BTW, you might have already guessed, our interest in Lustre is to use is
more like a shared general purpose filesystem. In that domain I believe
LVM is quite handy for an administrator to move around storage as need
under different volumes. Wondering whether Lustre could still provide,
if not exactly the same, but similar capability.
thanks,
Sridhar
________________________________
From: Peter Braam [mailto:[EMAIL PROTECTED]
Sent: Tuesday, January 09, 2007 5:18 PM
To: Sridharan Ramaswamy (srramasw)
Cc: cliff white; Nathaniel Rutman; lustre-discuss@clusterfs.com
Subject: Re: [Lustre-discuss] Logical volumes over Lustre
storage
Hi
You can also put your OST's on LVM's and get some flexibility
wit resizing, but probably you had already figured that out!
- Peter -
Sridharan Ramaswamy (srramasw) wrote:
Nathan, Cliff - Thanks for the clarification!
Think I understand this more now. Lustre can grow at the
granularity of
LUN size by adding it as another OST. Not in between. I
presume the
scenario is same for reduce/decreasing(take an OST
offline and add to
another MDT).
- Sridhar
-----Original Message-----
From: cliff white [mailto:[EMAIL PROTECTED]
Sent: Tuesday, January 09, 2007 11:21 AM
To: Nathaniel Rutman
Cc: Sridharan Ramaswamy (srramasw);
lustre-discuss@clusterfs.com
Subject: Re: [Lustre-discuss] Logical volumes
over Lustre storage
Nathaniel Rutman wrote:
Sridharan Ramaswamy (srramasw) wrote:
Is it possible to get traditional LVM
like functionality
over Lustre
based storage?
My understanding is Lustre can aggregate
storage OSTs to provide a
single mount point. But the aggregate
storage it provides can't be
carved out into different logical
volumes, is this correct?
For eg, assume each OST is 8GB
node1: OST1, OST2, MDT
node2: OST3, OST4
Using *single* Lustre instance is it
possible to provide two mount
points with 16GB each? And ability to
administratively change the
storage available to each of those mount
points, say
instead of 16GB
each to 20GB and 12GB. Something similar
to lvextend, lvreduce.
As Nathan mentions below you will be able to
dynamically add
OSTS in the
future. However, you can _not split a single
partition between two
filesystems (which is possible with LVM) so you
would not be
able to split the 8GB LUN. You could start with
16GB, add an 8GB LUN
and grow to 24GB, (You can do this today, but
you have to stop the
filesystem to change the config) but you could
not add 1/2
the LUN. So a
12GB/20GB split with 8 GB LUNS is not possible,
and will not
be possible
in the future.
cliffw
I presume you can achieve something like
the above by creating two
Lustre instances(running in different
ports) and mount
them separately
as 16GB filesystem. But that seems too
much overhead.
They don't have to run in different
ports, but yes, you can
achieve what
you want by making two different Lustre
filesystems. That
does mean you
need two different MDTs. (Similarly,
you would have to have two
different filesystems on your LVM.)
In Lustre 1.6 you can dynamically add
OSTs to a filesystem
to increase
the space available.
Appreciate any insights on this area.
thanks,
Sridhar
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