Musings on IT, data management, whitewater rafting, and backpacking

Monday, February 7, 2011

Offsite backup scenario TCOs

Calculated three year Total Cost of Ownership (TCO) for several backup scenarios and our environment and requirements.

Short version:
  • Tape still rules
  • SOHO disks are competitive
  • Enterprise disks are at least 2 times more expensive
  • Amazon S3 cloud storage is 8-10 times more expensive
  • Cost isn't everything
I read this Clipper Group paper In Search of the Long-Term Archiving Solution – Tape Delivers Significant TCO Advantage over Disk, and was blown away by their analysis.

I didn't believe that tape could be so much cheaper than disk. I decided to analyze various scenarios for my own setup.


Your environment and requirements will be different.

Here are the 3 year TCO results, from simple and local, to complex and remote:

$47,000 – LTO-5 tape loader on each server

$45,000 – Servers share local LTO-5 tape library server using Gigabit Ethernet

$51,000 – Servers share local LTO-5 tape libraries using Fibre Channel

$45,000 – Remote LTO-5 tape server

$44,000 – Remote Drobo-based disk server

$120,000 – Remote enterprise disk server

$497,000 – Amazon S3 cloud storage

$341,000 – Amazon S3 Reduced Redundancy Storage

$339,000 – Amazon S3 RRS using Import/Export for backups

I used list prices from well-known vendors, and Amazon's online S3 calculators.  We never pay list prices for servers, disks, and tapes, so this makes Amazon S3 look even worse.

The first five options are about the same in TCO.  Choosing between them comes down to other factors.

Enterprise disks are notoriously overpriced compared to consumer disks.  Sometimes you get what you pay for.  Sometimes.

I am astounded at how many times more expensive the Amazon S3 options turned out.  At Amazon's scale, they should be able to beat retail prices easily.  I'm not seeing that in our environment.

Each of these scenarios has pros and cons which are not captured in TCO.  I might discuss those in a future blog post.

Assumptions:
  • Offsite backups of five servers, 20 TB net available storage each.
  • Offsite backups ramp from 50 TB to 144 TB, in months 1 to 36.
  • About 4 TB per month incremental backups.
  • 1 TB per month restores.
  • RPO about 30 days.
  • One year disaster recovery, i.e. save base plus one year of incremental backups.
  • No server rent or power costs.  Those come out of Someone Else's Budget (SEB).
  • Free offsite server space and power – SEB.
  • No tape transport or storage costs – SEB.
  • Gigabit Ethernet WAN and Internet link.
  • No incremental WAN or Internet costs – SEB.
  • Replace everything after three years.
  • System administration costs roughly equal between options.
  • Backup software costs roughly equal between options.
  • Buy everything up front, including tape cartridges, except ...
  • Buy Amazon S3 services as needed.
  • No time value for money.
These assumptions roughly fit my environment and requirements.

Your assumptions will be different.

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