Lustre discuss - Jun 2007 - minimal high available lustre installation

What is the minimal high available lustre installation.

Is a two node lustre installation considered stable?
i.e.
node1: MGS+MDT+MDS+DRBD(for MDT/MGS)+OST+OSS+client
node2: MGS+MDT+MDS+DRBD(for MDT/MGS)+OST+OSS+client

If you add a third/fourth node, I would assume it would be just:
node3: OST+OSS+client
node4: OST+OSS+client

Is there any reason why this wouldn''t work for a high available
cluster?
Is there a better way to configure a small cluster?


Thanks,


Jon.

On Jun 21, 2007  22:26 -0500, Jon Gabrielson wrote:
> What is the minimal high available lustre installation.
> 
> Is a two node lustre installation considered stable?
> i.e.
> node1: MGS+MDT+MDS+DRBD(for MDT/MGS)+OST+OSS+client
> node2: MGS+MDT+MDS+DRBD(for MDT/MGS)+OST+OSS+client
> 
> If you add a third/fourth node, I would assume it would be just:
> node3: OST+OSS+client
> node4: OST+OSS+client
> 
> Is there any reason why this wouldn''t work for a high available
cluster?
> Is there a better way to configure a small cluster?
If you want a highly-available 2-node cluster then Lustre probably
isn''t
what you want.  If either node fails it is considered a "double
failure"
from the Lustre POV (both MDS, OST, client failing at once) and recovery
from this will not work.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

> If you want a highly-available 2-node cluster then Lustre probably
isn''t
> what you want.  If either node fails it is considered a "double
failure"
> from the Lustre POV (both MDS, OST, client failing at once) and recovery
> from this will not work.
I''m not wanting a HA 2 node cluster, I''m actually wanting a
HA 4 node cluster.  DRBD by itself works quite nicely as a 2 node
cluster but it doesn''t support 4way only 2way.
That''s the reason I was asking what the minimum lustre cluster size
was.
The docs mentioned that people are using a 4node cluster in production.
What configuration would you use for a 4 node cluster?

Thanks,

Jon.

> On Jun 21, 2007  22:26 -0500, Jon Gabrielson wrote:
>> What is the minimal high available lustre installation.
>>
>> Is a two node lustre installation considered stable?
>> i.e.
>> node1: MGS+MDT+MDS+DRBD(for MDT/MGS)+OST+OSS+client
>> node2: MGS+MDT+MDS+DRBD(for MDT/MGS)+OST+OSS+client
>>
>> If you add a third/fourth node, I would assume it would be just:
>> node3: OST+OSS+client
>> node4: OST+OSS+client
>>
>> Is there any reason why this wouldn''t work for a high
available cluster?
>> Is there a better way to configure a small cluster?
>
> If you want a highly-available 2-node cluster then Lustre probably
isn''t
> what you want.  If either node fails it is considered a "double
failure"
> from the Lustre POV (both MDS, OST, client failing at once) and recovery
> from this will not work.
>
> Cheers, Andreas
> --
> Andreas Dilger
> Principal Software Engineer
> Cluster File Systems, Inc.
>

On 6/23/07, Jon Gabrielson <jonyahoo@directfreight.com>
wrote:
> > If you want a highly-available 2-node cluster then Lustre probably
isn''t
> > what you want.  If either node fails it is considered a "double
failure"
> > from the Lustre POV (both MDS, OST, client failing at once) and
recovery
> > from this will not work.
>
> I''m not wanting a HA 2 node cluster, I''m actually wanting
a
> HA 4 node cluster.  DRBD by itself works quite nicely as a 2 node
> cluster but it doesn''t support 4way only 2way.
> That''s the reason I was asking what the minimum lustre cluster
size was.
> The docs mentioned that people are using a 4node cluster in production.
> What configuration would you use for a 4 node cluster?
1 MDS node
1 MDS failover node
1 OSS node (however many osts)
1 OSS node  for ost failover -- do note that the osts can be primary
on either of the OSS nodes.

This would be the absolute minimum I think -- clients are of course
separate. This is for 1.4.x, I am not sure how requirements and
prerequisites have changed for 1.6.

-- 
Mustafa A. Hashmi
mahashmi@gmail.com