why isn`t local storage suitable for hosting large storage volumes?
Uh... because it's local, and RAID controllers in a physical box aren't designed for MULTI user? They are smaller machines, lets not forget, and they are NOT really designed for Virtual Machines, they are getting better, but SAN devices are ideal for LARGE, Multi-Access data points. That's what they were made for. There is a reason that a physical box is 1% of the price of a typical SAN solution, that's not an accident, otherwise everyone would simply put their data on physical boxes and skip SAN altogether. Sure you can do it, but that storage you are talking about SATA.. I can tell you you have never even tried to host many VM's on a SATA RAID, go ahead give it a shot... When you start the 4th VM and the rest of the VM's come to a COMPLETE crawl, don't say I didn't warn you. Yeah, it's cheap... but not good performance, and it's worthless for anything but long term backup storage.
can have Terabytes with that. for much less than a 1000 bucks.
go for it. Don't complain when that $1000.00 4TB local storage isn't good for much more than MP3's and Photos.. good luck with that.
you mean, because EMC is a SAN company, they want me to have a SAN for large storage?
NO, that's that way it's ALWAYS been. Read up on Raw Device Mapping. It's for LUN's.it was intended for LARGE SAN's (that's who designed it, those big EMC / Netapp Companies), and since RDM's usually are 300-500G or bigger, when they came up with the idea it was at a time when local storage was 9GB SCSI drives... Think back 10 years, how far have we come? consider technology we use, and HOW it was implemented.. nothing has changed -- EXCEPT -- things are cheaper now, there haven't been any real big advances in hardware technology, not really.. things got faster, cheaper, and more of them (cores aren't really that fast, there are just more of them on a single die which comprises the speed). So SAN technology is like mainframes it existed LONG before anyone thought of Virtualizing.
Now when SSDD drives come down, NOW you will see changes to local machines, because with Dunnington (6 core) or 12 core by then, these "small" machines will become self sustaining portable SAN solutions...
come on !
Calm down, it will be ok. I didn't say I liked it, I am saying that's why. RDM is a LUN element, when or where have you EVER seen RDM in a RAID configuration, hmmmm? Yeah Show me a local SCSI RAID that has this option, you won't find it.. because as I said at the outset it's a SAN Terminology.
