hi,can anyone tell me where exactly DAS/NAS/SAN is implemented.

DAS

Directly attached to server, sort of 1 to 1.  Alot of SAN devices can be used as DAS, but now a days the way storage is growing, and with all the high availabilty features within operating systems (e.g Vmare ESX) which make use of SAN environments or shared storage, alot of companies are putting in SANs.

NAS and SAN

Celerra is a good example.  EMC call it Unified storage because it can have both.  So for example, imagine a University, with lots of physical File servers.  They could use the NAS part of Celerra (CIFS or NFS), and get rid of those physical servers, and host the File servers inside the Celerra. Save lots of physical space, and cost. Now they just create some Shares in the Celerra (CIFS or NFS), and everyone can connect to the shares just like before, and the students  won't even realise that there's been a change (probably because they are too busy getting drunk). They connect to their files, home directories just as before.

Second, the university have databases like Exchange (email servers), SQL servers, which need performance (number crunching).  If the University also bought the Fibre Channel option for the Celerra (or they could also use ISCSI here), then they can host the databases using what we call Block Level storage. They will need some dedicated hosts/servers attached to the Celerra via either Fibre Chanel or Iscsi, so these servers will be on a SAN, no NAS here.

Those are pretty cut down explanantions - any help ?

I certainly don't profess any expertise in this area, but came across an article that might help.

This is an interesting conversation, at least for me. And if I may, I'd like to weigh in on it just a little.

I have good understanding of the DAS/SAN options and which is practical and which is functional. But with the NAS, the considerable benefits I am seeing from a NAS are:

1) Multi-platform access -- this is something that is probably more common than I see in my environment. We are primarily talking about a file server and we would just assume run that through an AD member server.

2) Optimized for File I/O -- a number of services are not running? But I have to ask, is the optimization any greater that I could accomplish by simply locking down a 2003/2008 server? As Mr. Meogi would say, "show me optimization".

3) Scalability -- we are currently considering a solution to archive medical imaging on a Centera about 1500 miles away. A local NAS Head does this well.

An arguement I have against file servers built on NAS heads is, the more data on the server (which a NAS can really handle the amounts of data), the longer it takes to back it up -- no matter what the archive bit's value. This is simply because the backup agent has to look at every single file to determine the archive bit and then backup it up as appropriate (my file server backups are in the lower 25% when it comes to backup performance). Now that is based on traditional backup strategies and not through snapshots and cloning, etc.

I guess, in summary, I have only been faced with one real example of the need for a NAS. When I hear file server, I think home directories and departmental shares. But when I came across a real reason for block level access via the IP network, NAS technology hit a home run.

I'm going to the ISM book this evening and re-reread the NAS section.

Bart

Thanks for the reply and the thorough answers, Simon. I have about a fair grasp at best on the technology, but as Johnny Five said, "More Input!"

I can't read enough of these posts.

Bart

Excellent reply John.

Great information, thanks.

Hope to see more of your wisdom as I plough thro my EMC Proven programmes.

Snippets like this help in the learning proccess.

Thanks for your input.

Geoff

I thought those of you active in this discussion may be interested in a new discussion that was started today by Stu Miniman, from EMC's CTO office. He's presenting an online seminar titled "The Journey Towards the Converged Data Center: Fibre Channel over Ethernet (FCoE) and iSCSI". He's looking for input frm the Proven Professional community on the topic in this thread.

Seems like a good a good seminar if you are interested in data center technologies.