> What is alternative to NFS if we implement Solidfire.
Well, you can continue using ONTAP and SolidFire from VMware.
If you're refreshing and are considering NetApp HCI or SolidFire as the new platform, it is possible to buy ONTAP Select and run as VM backed by SolidFire iSCSI storage.
If you have a lot of files to share or need high throughput, it's better to use physical ONTAP appliances, but if it's a small to medium environment, if you move the bulk of VMs to iSCSI then maybe you'd have just plain user homes and profiles on NAS for which ONTAP Select is likely to suffice.
> 2. For FAS storage cluster, and a lot of VMware VM's, what is the general procedure to migrate all data over?
Add a NetApp HCI or SolidFire back end, use PowerCLI to run something like
You can move VMs in batches like this, but it's better and safer to move them one by one and make sure it works as expected (because you may have snapshots and whatnot at Source).
So it'd be good to check vSphere docs for the version you have as well as various VMware KB articles.
I'd be especially careful with wildcards i.e. trying to Storage vMotion many VMs at once - it's best to do 1-2 at a time and move busy and large VMs in off-hours. I think PowerShell makes that easy.
If you have VMs you want to retain on ONTAP and if you have ONTAP Select running on NetApp HCi or SolidFire, you could possibly use SnapMirror (assuming your ONTAP version is 9.5+) to replicate VMs from current to new (virtualized) VM. But personally I'd prefer PowerCLI-driven Storage vMotion as it's granular and there are no big switch-overs.
There's also a way to use "reverse" SnapMirror between SolidFire and ONTAP, i.e. normaly SolidFire's implementation of SnapMirror is used to replicate data from SolidFire to FAS for DR/BC, but you could use it for migration of iSCSI FlexVols (not NFS shares). It also requires a bit more knowledge so I'd still recommend PowerCLI because it's easy to understand and use. If you have a large amount of data (> 300 VMs, for example), then those special method may prove valuable. Maybe get NetApp PS or Partner to provide this service for you.
This is a large VM's environment (+2000), all based on NFS datastores, which can benieft from NFS's advantages, easy to provision etc. HCI/SolidFire change the datastore infrastructure to iSCSI based, how can I know it will be better than NFS, and particularly in performance perspective in such dynamic workload enrioment, oracle, SQL, NFS and CIFS?
It's quite subjective, I think. Some people prefer one, some the other and some use both (and put certain workloads on one, others on another, depending on preferences, requirements, etc.).
Both ONTAP (flash-based) and Element (SolidFire) provide storage QoS and storage efficiencies, so you'd get space savings and be able to consolidate different workloads on one platform (by using QoS). Both are convenient to use. ONTAP definitively has more features, but it also requires more expertise to make use of them. If you have some particular "must have" feature that depends on ONTAP or NFS, then it may be better to not change. Backups for 2K VMs would be slower on SolidFire, depending on what s/w you use (from my experience Veeam and CommVault work very well with SolidFire and can backup in parallel.)
If your current system is under maintenance, you could download a free SolidFire Demo VM (under Tools, find Element Demo VM) and provision it as a VM. Then (vid below) you can set up a single-node SolidFire cluster, and can get the idea of how it works (vid at the bottom). If you don't mind to try without vCenter you'd just need another (nested) ESXi - no need to install vCenter plugin and vCenter itself.
Or, to save time, get a NetApp partner or SE to show you remotely in NetApp Lab on Demand, I think in 15 minutes you'd know if you'd like to work with SolidFire iSCSI. SolidFire PowerShell Tools are also quite easy to use if you're into PowerShell.