[Lustre-discuss] MGS and MDT on Failover Pair

[Cliff White]

Brian J. Murrell wrote:
> On Wed, 2008-09-10 at 16:23 -0400, Roger Spellman wrote:
>> I am building a system with a redundant MDS, that is two MDS sharing a
>> set of disks, one being Active, the other Standby.
>>  
>> If I put the MGS and MDS on the same system, it appears that they must
>> be on the same partition as well.
> 
> No.
> 
>> Otherwise, when there is a failover, the MGS will not fail over.  Is
>> that true?

If the MDT and MGT are separate partitions, then you will have to fail 
them over as separate services, as each partition will be mounted 
separately. The separate partitions can be on one system. Of course any 
decent HA tool will allow you to failover multiple services with one action.

Should note- the MGS is very small, and only used for configuration 
changes, and mount information. If all your clients are already mounted, 
an MGS failure is quite transparent - you can run for quite some time 
with a dead MGS.

For a very robust system, I would suggest moving the MGS to a small 
machine (heck, a cheap laptop would work for all but the biggest sites)
replicate the MGT disk and put your failover dollars on the MGS.

You could build a very robust failover MGS for the cost of two cheap
whitebox PC's (modulo network hardware cost). Also, a separate MGS is 
recomended when you have more than one filesystem.

cliffw


> 
> Not true.
> 
> b.
> 
> 
> 
> 
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