Hello Vijay, that depends on the type of Raid that you will be using as well as the type of data.  In most cases that I have seen most customers create 2 VD instead of one large one.  The biggest reason is the rebuild time, as with a 18TB VD the rebuild time will be long.  Please let us know if you have any other questions.
Hello, I have MD 3220i with 24 sas drive with raid 6 setup. Now i have purchasednew Dell MS 1220 expansion san with 24 sas drive  and attached with MD 3220i.So now can you please guide me for setup to get best IO permanence .Spec.HDD Detail : 6 Gbps, 10k, space per disk 1.2 tbDisk pools:1Virtual Disks on Disk Pools: 2Disk groups:0Access virtual disks:1 Thanks, Vijiay
Best practice for expand MD 1220 with MD 3220i San