Advice for moving web/email from dedicated (2.2GHz Celeron/1GB/140GB) to VPS (Linux/CentOS)

I'm considering moving from a dedicated server to a VPS solution for email hosting for multiple domains/clients. I've already set up some VPS instances with ServerPoint.com to do spam/virus scanning for me, and now I'm ready to move away from my dedicated machine. ServerPoint had 2 hours of downtime last weekend to do scheduled maintenance on one of their machines -- I need a provider with shorter outages than that.

The problem is that I need lots of disk space (150GB to start, grow to 200+GB) relative to my CPU and RAM requirements. All of the VPS providers I've looked at (Linode, Slicehost, A Small Orange, Rackspace) offer fixed plans without the ability to add disk space. If I'm reading my MRTG stats correctly, I'm sending about 10GB out per day (I need to calculate how much of that is off-site backups).

Should I be looking at Amazon EC2 with S3 for storage? Looks like monthly fees of $15 for 150GB storage, $45 for 300GB transfer, $20 to reserve a "Small" instance and $21.60 for actual usage might fit my needs, and allow for growth. What do I need to know before going down the EC2 path? Reliability? Possible data loss? Backups to S3?

Are there other options?

EDIT: Additional details: Linux (currently Fedora, planning to use CentOS) with qmail, vpopmail (virtual domains), QmailAdmin (web interface to vpopmail), SpamAssassin, ClamAV, dovecot (IMAP). About 200 domains hosted.

From serverfault tomlogic

• You have not given any detail regarding your setup and what it is exactly you are currently running. Is this a linux machine with local maildir storage etc or is this a Windows Server running exchange etc.

  Moving to Amazons ec2 and s3 is not a something you should move to without planning out your requirements and how it fits into Amazon's offerings, which are quite different to the standard server and VPS offerings from the likes of Rackspace etc.

  EG: S3 is not 'mountable' from the server in EC2. It is block storage and the primary interface to pulling and pushing content is HTTP POST and GET's! . EC2 Servers are reboot able but if it dies the server is gone.! ( There is now a work around for this which is to use EBS volumes for local storage but again this needs to be part of you design)

  Not a full answer I know but I have seen many people attempt to treat AWS products just like any other hosting/server provider and loose data because they did not understand the caveats.

  Unless you are looking to take all of this on I would stick with one of the more 'traditional' providers.

  HTH.

  tomlogic : How can I learn more about EC2, using EBS for persistent storage, and the general limitations of this setup? Could I use EC2 with EBS, and have a fixed IP that doesn't change for years? Is there a site or forum where I can get advice on Amazon's offerings?
  From MartinP