Advice about storage purchase decision - DAS vs NAS vs SAN

Greetings and thanks in advance for taking the time to help us with this critical decision.

Currently we have: Windows 2008 Dell server connected by SAS cable to a MD3000 storage (DAS)
It works as a http server to server files that amounts to a total of 15TB so far.

We are running out of space quickly and need to act now.

The volume is at its maximum limit now due to the way it was formatted initially - so attaching a MD1200 to extend the storage wouldn't work (we'll not be able to extend the volume

We are evaluating if we should get the new unit to be NAS vs SAN vs DAS.

DAS seems the simplest of them all, least complex and the the one with least possibility of bad configuration.

It can support up to 8 servers connected with single cables.

So, would you recommend we switch to an ISCSI SAN, DAS or NAS?

I'll follow up with whatever details would help you give a relevant advice to our specific case.

Thanks again
Mohamed HammadAsked:
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andyalderConnect With a Mentor Commented:
I missed this bit - "We don't even have 8 servers yet - it is a single server which we aim to make high available by adding a 2nd."

If you're going to have two hosts attached to the same LUN with clustering an MD3000/3200 SAS attached SAN would be needed. There's no storage level replication though for a remote site, you would have to do that with software on one of the servers. would do that for you.

MD3260f does remote replication but that's a lot more expensive.

By the way, another slightly misleading description on Dell's site is the "up to 8 servers", it does indeed support 8 servers connected by SAS but because there are 4 ports on each controller you can only share a particular LUN between 4 servers, not that that will be a problem in your case.

Still can't quite see why you can't hang a couple of additional enclosures on your current MD3000. Even if you can't expand the current LUN due to some software restraint you can create another bigger LUN just like you would be doing with this new storage box.
Patrick BogersConnect With a Mentor Datacenter platform engineer LindowsCommented:

It depend on several things. A simple NAS which is attached to the network wont be fast enough to serve up to 8 servers simoultaniously.
DAS can, so could SAN but here the question lays "what is the budget?"

If budget is big and number of IOPS is very high i would say fibre optics and SAN.
If budget is not sufficient go for DAS.
Mohamed HammadAuthor Commented:
If the budget is tight - would you recommend a cheaper SAN like the MD3xxi - or is it like, either an EqualLogic or better go to DAS?

We don't even have 8 servers yet - it is a single server which we aim to make high available by adding a 2nd.
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Patrick BogersDatacenter platform engineer LindowsCommented:
If budget is an issue i would say more is better in terms of space.
So if the DAS solution has been performing ok there is no need for iscsi/fiber san.
DAS is cheapest but "It can support up to 8 servers connected with single cables." describes what most people would all a SAS attached SAN, not DAS. DAS is generally considered to be a dumb shelf connected to a RAID controller inside the server and is the cheapest and best solution for a single server.

The MD3000 is generally considered to be a SAS attached SAN as it's shared storage. Dell may describe it as DAS on their website but the real manufacturer describes it as SAN - (actually the MD3000 is LSI Engenio but they sold the range to NetApp who still make later versions for Dell, IBM etc).

You will not get better performance from a SAN than from a DAS, at least if you have the same disks in each. Why would separating the RAID controller from the server with a bit of fibre optic cable speed it up rather than plugging it directly into the PCIe bus?

As far as real DAS is concerned the MD1000 range of expansion enclosures run on Dell PERCs just as well as they run on MD3000s.
Mohamed HammadAuthor Commented:
So what would you recommend David?

SAS attached SAN - MD ISCSI SAN - EqualLogic ISCSI SAN?

We would love to be able to remotely replicate the volumes to another site but I guess that can be done with a SAS attached SAN - right?
Mohamed HammadAuthor Commented:
It would work actually - thanks a lot :)
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