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From:Stewart Smith Date:July 13 2005 7:32am
Subject:Re: can mysql use the shared-storage .
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On Tue, 2005-07-12 at 09:34 +0200, Martino Piccinato wrote:
> Stewart Smith wrote:
> 
> > MySQL
> >Cluster lets you work out your disk bandwidth requirements per-node for
> >the checkpoints. It is extremely unlikely that you're going to need high
> >bandwidth for this, so you save a heap on storage.
> could you please explain better this latter thing? I can't exactly 
> understand what you mean.

For MySQL Cluster, you can work out your approximate MB/sec requirements
for disk. Generally, this isn't much and will be satisfied by only a few
commodity disks. Fibre channel storage arrays cost more (and you're
going to have local disk anyway)

> As for shared nothing/shared everythin approach it is certainly true 
> that shared nothing approach is better for hardware failures but it is 
> also true that for shared nothing:
> 
> 1) adding nodes to the cluster means repartiotioning (redistributing) 
> datas on the nodes, how expensive (I mean CPU cylce cost...), difficult 
> and errore prone is this operation for mysql cluster?

It helps if you don't support online adding of nodes :)

To add a node (currently) you take a backup, shutdown, start a new
cluster and restore.

> 2) CPU processing power is not used optimally as in shared mode: single 
> query operations are carried by different CPU based on data 
> partition/availability on the different storage the CPU is linked to and no

I'd argue that - I'd say both can do equally as well at balancing load.

> I also wonder whether for really bug storage needs buying a shared disk 
> array shared by some of the nodes could be cheaper than buying 
> additional nodes with dedicated storage. One could use one shared 
> storage for each n/x cluster nodes of n nodes cluster. This is clearly 
> just an ecnonomic (€) consideration as ths system wouldn't affect 
> performance at all.

But remember, it's an extra $2k per node just to attach to existing
storage (HBA and switch port costs)! I can buy a couple of TB for that
sum.

You will also have to start to carefully think about disk bandwidth too.
Fibre Channel generally tops out around the 250MB/sec mark. 10 machines
with a single disk in each are going to have a lot more total bandwidth.
-- 
Stewart Smith, Software Engineer
MySQL AB, www.mysql.com
Office: +14082136540 Ext: 6616
VoIP: 6616@stripped
Mobile: +61 4 3 8844 332

Jumpstart your cluster:
http://www.mysql.com/consulting/packaged/cluster.html

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Thread
can mysql use the shared-storage .huang mingyou12 Jul
  • Re: can mysql use the shared-storage .Stewart Smith12 Jul
    • Re: can mysql use the shared-storage .Martino Piccinato12 Jul
      • Re: can mysql use the shared-storage .Stewart Smith13 Jul