can an EMC AX4-5i support 2TB SAS Drives?

SATA 7,200 RPM performance will be poor compared to SAS 15,000 RPM drives.

so what is the difference between SAS 15k drives in Raid 5 compared to SATA 7200 drives in RAID 10?

or SAS drives running at 7200 RPM

The more drives you have the more IOPS you get, regardless of the speed of the drive.

7,200 RPM SATA drive - Approx 50 IOPS
15,500 RPM SAS drive - Approx 200 IOPS

ok so if one builds smaller arrays?

Have a read of this article

https://www.experts-exchange.com/questions/26104923/IOPS-question.html

Check the article, because different RAID technologies have different Write Penalities, e.g. RAID 5 - 4, RAID 10 - 2.

Max Performance = Max Spindles = More Performance SAS, and RAID 10.

If you know the specfications of all the drives you will be using you will be able to calculae the exact IOPS for thr SATA and SAS drives, and complete the calculations between RAID 5 and RAID 10.

and again the performance difference between a RAID5 array of 15k drives vs. a RAID10 array of 7200k drives...

The 2TB SAS drives out today are enterprise SATA drives with the SAS electronics.  Outside of the inherent benefits of SAS over SATA, intelligence, and larger queue depth, the performance advantage over the 2TB SATA disks are nominal.  So even IF they worked, you would not see much of a performance advantage under most workloads.

Which leads me to part II.  You can't just slap in 2TB SAS drives and expect them to work.  They won't.  EMC's controllers will reject them.

The difference is the DISK, SAS always provides more IOPS per disk than SATA.

SAS 7,200 or 15,000, you would need to check the real specs, or calc the IOPS per disks, some enterprise disks the IOPS per disks are given.

So you can see if you change the RAID 10 of SAS, the IOPS is going to increase because of half the Write Penality of RAID 5.

Respectfully, EMC uses constellation. drives. The 2TB SAS & 2TB SATA performance are nearly identical.  The controller disables the write cache, and controls the queue depth. Read-ahead is turned off.  Only a few MB/sec on throughput, and that is due to the nature of the interface.

In this case you will NOT get more IOPS with the 2TB SAS even if they did support it over the 2TB SATA.  Certainly the 600GB SAS has better numbers then the 2TB SAS, but you didn't ask about that.  

they want  to sell me the 600gb SAS drives - i just want to find out whether i can keep something close to our current performance with different raid levels give or take 1/3 - ultimately it is a question of how much dough i can get approved so if i go with slower drives in a better raid configuration and not lose any perceivable performance by the end user then i'm going with the EMC approved 7200 disks in a raid 10 config and I'll bet the family farm that 90% percent of end users won't see much of a difference but mu redundancy /FT will be something i can count on

andwhy won't the 2TB SAS disks work on the AX4-5i again?

Because EMC hasn't created (or isn't shipping) a 2TB SAS disk with the appropriate firmware.  As such, the "product" doesn't even exist.

they said the same thing with the AX 100 and 250gb drives but i got 500gb drives working just fine 3 or 4 yrs. ago

fair enough - thanks for the information...  For the record I wasn't thinking of putting just any drives in there - My rep at CDW had spec'd these out - Mfg#: EMX-V3-VS07-020-6   -  (2TB SAS drives for EMC) but it seems they are not for the AX4  but for the VNX  so EMC HAS these drives and they ARE shipping them but only for newer products.   I certainly want to make the right decision but I work for a company that doesn't like to spend money at all but they certainly like to blame you if things go wrong.  Oh wait that's almost every company...

By the way those AX100's I mentioned before are still running strong today with 2x the capacity they were supposedly designed for.

One absolute in the storage 'biz ... every year you can count on faster, cheaper, better.  So buy absolute minimum you need when you need it.  The 2TB, 3TB, and 4TB disks will eventually be supported. it is inevitable.   Buy as little as you can get away with today (that is supported), then wait it out.

well from the sounds of it i'm screwed and have to go with the 600gb SAS drives if i want to get any performance.  And I have to use RAID5 if I want to squeeze as much capacity out of them as I can...

It doesn't look like I can get decent enough  performance from the 2TB SATA Drives in RAID10  if the calculation above is any indication.

Now, SATA always has had poor performance. But it depends what performance you require.

I want to use the SAN as my datastore for Virtual Machines (ESX 4.1) The virtual machines would be a combination of web servers and database servers.  Not a lot of traffic on them except during the beginning of every term - (we host the websites for several universities around the country -we sell mostly textbooks and  some merchandise.  

thanks!