[Lustre-discuss] Lustre and iSCSI

[David Pratt]

Hi Andreas. NFS is fine for XenServer so think it is worth evaluating  
Lustre as a proof of concept for storage pool. First step I want to  
take is to setup a single node (everything on the one node as you have  
identified) to ensure XenServer can properly connect to NFS through  
Lustre.

Beyond that, I'd be interested in assembling more nodes in some HA  
configuration to obtain read performance in neighborhood of 100-200MB/ 
s and writes of 25-50MB/sec. Not quite sure how many nodes that would  
take. In any case, hoping these sort of numbers are not too pie in the  
sky. My understanding is that adding more nodes will not only increase  
storage volume but speed.

Will be looking through documentation for an all on one node install  
for first part of evaluation. Many thanks

Regards,
David


On 4-Aug-09, at 11:22 AM, Andreas Dilger wrote:

> On Aug 04, 2009  09:58 -0300, David Pratt wrote:
>> Hi. Many thanks for your responses. Generally, the qualities of  
>> Lustre
>> appear great for a Storage Repository for virtual machine images in
>> XenServer since you would get a combination of fault tolerance, a
>> pretty much infinitely scalable distributed storage pool, speed and
>> ability to migrate virtual machines across a number or hosts.
>> XenServer can use NFS, iSCSI, NetApp, EqualLogic or Fibre Channel
>> storage repositories at this point. It appears there is some
>> capability to create a plugin to allow for others. It is possible  
>> that
>> the only way to get Lustre to work would be with the development of a
>> plugin.
>
> You can re-export Lustre via NFS to these clients.
>
>> At this point, to create a minimal Lustre install to play
>> with, how many machines will be required?
>
> Depends on how available/robust you need the system.  A "functional"
> system can run on a single node (MDS+OSS+client+NFS server).  A
> highly available system needs at least 3 nodes (MDS, OSS, client 
> +NFSd),
> with the MDS and OSS doing failover for each other.
>
> That said, unless you plan to scale beyond this (i.e. multiple OSS
> nodes) you could just use a pair of nodes for an HA NFS configuration,
> which is arguably less complex.
>
>> On 3-Aug-09, at 8:01 PM, Klaus Steden wrote:
>>> Hi David,
>>>
>>> I did some experiments last year with Lustre 1.6.x and a Dell iSCSI
>>> enclosure. It was a little slow (proof of concept mainly) due to
>>> sharing MDT
>>> and OST traffic on a single GigE strand, but as long as the
>>> operating system
>>> presents a valid block device, Lustre works fine.
>>>
>>> hth
>>> Klaus
>>>
>>> On 7/31/09 11:13 AM, "Cliff White" <Cliff.White at Sun.COM> etched on
>>> stone
>>> tablets:
>>>
>>>> David Pratt wrote:
>>>>> Hi. I am exploring possibilities for pooled storage for virtual
>>>>> machines. Lustre looks quite interesting for both tolerance and
>>>>> speed. I
>>>>> have a couple of basic questions:
>>>>>
>>>>> 1) Can Lustre present an iSCSI target
>>>>
>>>> Lustre doesn't present target, we use targets, and we should work
>>>> fine
>>>> with iSCSI. We don't have a lot of iSCSI users, due to performance
>>>> concerns.
>>>>
>>>>> 2) I am looking at physical machines with 4 1TB 24x7 drives in
>>>>> each. How
>>>>> many machines will I need to cluster to create a solution with
>>>>> provide a
>>>>> good level of speed and fault tolerance.
>>>>>
>>>> 'It depends' - what is a 'good level of speed' for your app?
>>>>
>>>> Lustre IO scales as you add servers. Basically, if the IO is big
>>>> enough,
>>>> the client 'sees' the bandwidth of multiple servers.  So, if you  
>>>> know
>>>> the  bandwidth of 1 server (sgp_dd or other raw IO tools helps)  
>>>> then
>>>> your total bandwidth is going to be that figure, times the number  
>>>> of
>>>> servers. This assumes whatever network you have is capable of  
>>>> sinking
>>>> this bandwidth.
>>>>
>>>> So, if you know the IO you need, and you know the IO one server can
>>>> drive, you just divide the one by the other.
>>>>
>>>> Fault tolerance at the disk level == RAID.
>>>> Fault tolerance at the server level is done with shared storage
>>>> failover, using linux-ha or other packages.
>>>> hope this helps,
>>>> cliffw
>>>>
>>>>> Many thanks.
>>>>>
>>>>> Regards,
>>>>> David
>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------
>>>>>
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>
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
>