[Lustre-discuss] one server node fails, its all dead?

[Kevin Van Maren]

On Feb 2, 2009, at 2:57 PM, Andreas Dilger <adilger at sun.com> wrote:

> On Feb 02, 2009  15:23 -0600, Robert Minvielle wrote:
>> So, if I have a server that goes down, the clients are out of luck.  
>> I have
>> a hard time believing this is "acceptable". Ok, so it is "as good  
>> as" NFS,
>> but I mean really, if a single storage unit fails all of my clients  
>> can do
>> nothing? Am I missing something here or is this by design?
>
> It is possible for clients to create new files while a server is down,
> but as you can expect it isn't possible to read any data from the  
> failed
> server.  In some cases users have used DRBD to do device replication
> instead of using shared storage.
>
>> The real reason
>> I ask is that I am testing Lustre against a few other DPFS to see  
>> if we will
>> move to Lustre. So far, some things are nice, and some are not  
>> nice. Writing
>> seems to be faster, but reading is slower (than my other test DPFSs).
>> Contacting Sun to ask about support took forever. At least four  
>> days for them
>> to just call me back and tell me they could not give me a price  
>> without
>> knowing how much storage I have (ugh, a pay per byte system, great).
>
> You can imagine that supporting the largest Lustre filesystem (1300+  
> OSTs
> with 10PB of storage and 30k+ clients) will take more effort than  
> supporting
> a system with a handful of OSTs and clients.  The support price is  
> not per
> client, but rather per-OST, IIRC.

Just to clarify: Lustre support prices are currently based on the  
number of OSS servers (machines serving OSTs), not the number of OSTs,  
and not the size of the storage.

>
>> So, Lustre users, is it worth it? My setup would be 24 OST's with  
>> about
>> 100TB of storage, 10G ethernet, RAID on each OST, at least 20 or so  
>> clients
>> needing pretty fast read/write, connected via 10G ethernet (yes, I  
>> know I
>> need a SAN but the physical locations will not allow it and the  
>> price is
>> prohibitive, hence my looking at DPFSs)... Am I on the right track  
>> looking
>> at Lustre, or should I go elsewhere? I also need commercial support  
>> of some
>> kind (although it seems Sun is unsure of themselves here, they did  
>> not
>> know who to contact when I contacted them "Lustre, we make a product
>> called Lustre? Hold please"...
>
> Well, Sun is a big company, and Lustre was only acquired a year ago  
> and
> does not necessarily generate a high call volume to the L1 support  
> people,
> so they are not necessarily going to have information immediately  
> handy.
>
> Note that Lustre itself does NOT need a SAN to work, unlike some other
> cluster filesystems.  The only SAN requirement is for failover pairs  
> of
> servers.

Sun also has low-cost shared storage options for Luster -- search for  
Sun Storage Cluster.

> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
>
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