New SAN Solution Recommendation Required

I just wanted to get your inputs on recommending the right SAN for customers.
What type of SAN do you recommend?
Should it be fibre or SAS drives?  
What type of connectivity (fibre or SAS)? What are the pros and cons?  
What is the total size? How much of is RAW and how much becomes usable?  (for example if the total size is 4 TB, how do we configure and how much becomes usable?)
What size drives?
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Typically a SAN is connected to the servers using fibre channel, the drives themselves are typically SCSI and these they are are SAS (Serial Attached SCSI).

Did you mean SCSI or SATA for the drives?

Then you have how the SAN connection to the server, which is normally Fibre Channel, but these days you can also have iSCSI (SCSI over Ethernet) or even Infiniband.

The amount of usable data depends on how you setup the SAN.  4TB of data means nothing.  The deciding factor on usable data is how many drives, how big the drives are, and which RAID option you choose.

Which size drives will depends on your goal.  To get the most data in a SAN you want the largest drives, however reading all of that data from a single SAN may take a long time or cause other performance problem if you have a lot of servers attempting to use the same SAN.
KarthickSethuAuthor Commented:
Thanks for your quick reply, that was useful!, I am more of an applications guy, so pardon my ignorance in this. The vendor asks whether we want DS3000 or DS4000, which one do you recommend from your experience?

So I should tell the vendor that the SAN will be connected to the servers using Fibre and drives will be SAS - is this right?

Again, on RAID, can we only have the whole SAN in only, one type of RAID? Can we portion of without RAID and portion of it in different RAID?
Well the DS4000 can scale bigger and is faster.  The problem is IBM has just (Dec. 2009) withdrawn this from marketing.  Meaning they don't sell it any more.  I'm not sure how much longer they will support it either, typically they will support hardware up to 5 years after it is withdrawn from marketing.

Here is the withdrawal letter:

It is being replace by either the DS3400 or the DS5020 depending on your needs.

I would check with your vendor about the support for the DS4000.  It is a fairly good device, we have one for our distributed side and we have a DS8100 that we share between our mainframe and distributed side.

The DS3400 can go up to 21 TB if you use SAS and 48 TB if you use SATA.  SAS typically performs better, but if you need more than 21TB you may need to go with SATA.  However those amounts are RAW data, not formated.

You can 'carve' up the SAN and have different RAID setup.  I don't do our SAN management, so I don't know technically limitations, I just know you can do this.
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madunix (Fadi SODAH)Commented:
don't forget to think about Disaster Recovery and BCP when you implement SAN solution, I have implemeted 3 sites replication using IBM technology DS8100 SAN storage. In my project I have SAN to SAN replication synchronous over Darkfiber (distance=5Km) with zero lost data, and asynchronous replication over MPLS with 35Mbps (distance=150Km)

"Metro Mirror is generally considered a campus-level solution, where the systems are located in fairly close proximity, such as within the same city. However, the distance supported will vary based on the write intensity of the application and the network being used. In general, with adequate resources, most customers find up to a 50-kilometer distance acceptable with some customers implementing up to a 300-kilometer distance."
"With Global Mirror, the target site may trail the production site by a few seconds. The frequency of creating a consistency group is a tunable parameter, and you?ll need to balance your recovery point objective with the performance impact of creating a consistency group. Many customers find a three- to five-second consistency group achievable (i.e., in a disaster, you?d lose the last three to five seconds of data)."
"The vendor asks whether we want DS3000 or DS4000, which one do you recommend from your experience?"

Are you a homogeneous IBM only shop today? If not I would strongly recommend that you consider options from 2-3 SAN vendors.  If nothing else you will see some options, and get some competitive bids, and get a bit more in-depth SAN education.  

Before I would make a particular recommendation I would ask you a few key questions:
1) Performance requirements (what is this being used for - virtualization, webservers, database etc.

2) Availability/Replication (do you need to create offsite/onsite backups with the SAN, how about site redundancy and recovery.  Is the ability to perform snapshots for point-in-time recovery important?

3) Capacity/Growth - how much usable capacity will you need today, what growth are you anticipating, will you add storage annually, with a particular budget cycle, or "as deemed necessary".  this will affect how much "extra" storage you buy today.  remember storage price per GB goes down over time, so if the SAN system doesn't require you to "over buy" too much today, it will be more cost effective over the long run.

"So I should tell the vendor that the SAN will be connected to the servers using Fibre and drives will be SAS - is this right?"

It depends on what this will be used for and if you already have a fiber infrastructure.  For many organizations iSCSI is a much more cost-effective connectivity because 1) they already have Gigabit Ethernet infrastructure, and have IT staff that knows how to work with it, and 2) Gigabit Ethernet infrastructure (nics, cables, switches) is significantly less expensive than fiber eq, and you can use your routers/firewalls for remote replication without buying specialty gear.  These days, unless you have specific requirements that indicate Fiber, it is much more expensive than some attractive iSCSI alternatives.

Drive types:
 Fibre or SAS (10k or 15k rpm): - High Performance, mission critical storage
 MDL SAS (7.2k) - Low-to Moderate Performance, these drives are manufactured for a good compromise of cost per GB with high availability.
 SATA (7.2k) -  low performance, archive/backups/test/dev, higher failure rates of drives usually relegate SATA to tasks with the lowest availability requirements.

"Again, on RAID, can we only have the whole SAN in only, one type of RAID? Can we portion of without RAID and portion of it in different RAID?"

RAID, and usable capacity is very dependent on vendor, make and model of SAN.  I am an HP reseller.  The LeftHand SAN I work with can be configured for various hardware levels of RAID, and optional network RAID (for replication and high availability).  All of these options have a significant effect on usable capacity, performance, availability, and ability to withstand (or recover from) various hardware failures.

For example sake take a look at this capacity calculator for our products:

You can see that the hardware RAID level will greatly affect the "usable capacity" for any of the listed SAN model.  This will be the case with any manufacturer, but each vendor offers different ways to configure RAID, either by the storage module, SAN, cluster, storage pool, LUN/volume etc etc.


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KarthickSethuAuthor Commented:
Very categorically responded for my questions.
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