Ok, I have no problem with tape. It’s a *GREAT* backup medium when your requirement is portability for massive amounts of data and you’re not replicating said data.
If I had to ship 400TB of backups to Iron-Mountain, to protect against the earthquake-to-end-all-earthquakes tape would be my FIRST choice (though maybe, as a GIANT CAVE – Iron Mountain might not be.) 😉
But… (and this is where it gets fun)
I have a customer who *LOVES* tape.
Wants to have it’s children loves it.
Uses it as primary storage loves it.
Now if you:
A> Have a few hundred terabytes of data to Archive.
B> Have millions of dollars to spend on giant room-sized storagetek libraries, and the space, power, and cooling that that entails.
C> Really love tape.
and most importantly
D> Live in the early 1980s
Then Archival to tape is *SO* the way to go.
The argument given is as follows. “Tape is cheaper than Disk”
Well yes, on a terabyte for terabyte scale tape might be cheaper…maybe if you exclude the hardware.
But if you throw something along the lines of EMC’s Atmos product, or even Centerra, or I’d even go so far as to say the NetApp box appealed to me at one point. (Now that the Celerra supports File Level Retention, I’ve been cured of that.)
Because when you throw in modern options like replication and, dare I say it, DEDUPLICATION, Disk rapidly becomes the better, faster, more cost effective way to store your long-term data.
Now I wouldn’t recommend anyone go out and buy a DMX-4 for Archival purposes.. (Though if you want to let me know ahead of time so I can buy some EMC stock. – I’m not currently holding any.)
I checked, and the only Tape vs. Disk comparisons I could find on-line were done by storage vendors, each of which has their own agenda (and big surprise, the analysis came out favouring whatever they were selling), so none of them are valid in the grand scheme of things. (I have a few things to say about marketing and statistics, but that’s a different post)
The things I look for when judging where to store data…
A> How many copies of the data do I need?
This is often overlooked and a question not asked. How many copies of a piece of data do you really need? And how many do you currently have? I’ve been in one data center recently where they LITERALLY have boxes of old tapes stacked up along the walls. (Note: Storing your backups WITH the system you’re backing up doesn’t do much in the event of a fire or natural disaster)
B> How long to I need to keep the data?
Retention policies are a big catch for a lot of people. For “Backup” purposes (see my last post) I say two full backups are all that is really required. If there is any kind of a likelihood that some critical corruption could be missed for weeks (or months) than adjust your backup strategy accordingly. (or find a better way of auditing your production data for errors)
C> Does my data have to be portable?
Ok, this is aimed specifically at Tape. The answer is this. If you have a remote DR facility and a high-speed connection between them, there is absolutely NO REASON to go to tape for portability. By virtue of Replication (whether it be the production data or VTL) you’ve already moved your data off-site. Now if you’ve only got one data centre and it’s sitting right on the San Andreas fault line (I’ve actually worked here – not joking) then send tapes off-site.
Lots of them.
5 or 6 times a day if you can.
D> Am I storing a copy of production or my only copy?
If you’re storing a copy of production (running) then chances are you’re not going to need the backup. If you’re protecting yourself against someone hitting the delete key accidentally, then maybe Celerra (SnapSure – periodic checkpoints that even the users can access themselves) or Centerra (Don’tEvenThinkAboutDeletingThis) are better options.
If you’re storing a copy of something so you can make room for something else, than backup tape is probably not your best option. Consider an archiving solution like Atmos or Centerra, or even a Celerra with File Level Retrieval enabled – and version 5.6.44 and later supports de-duplication (both single-instance storage and compression) natively.
E> Do I have the money to spend now, or am I willing to spend more over time to keep the initial investment down. (This is a valid question – and I’d like to know if anyone has any ideas on which would be the cheaper initial investment.
Just remember that you have to count the floor-space as well. Something many people forget when scoping out storage buys.
if I want 150TB of storage and I want to do it with tape, what’s the supporting hardware going to cost me? (A single CX4-240 with one rack of disks can provide up to about 220TB of storage with current drive-sizes.
A final note. Remember with any “portable” backup solution that you have to keep your backups safe. Tapes, like disks, don’t respond well to things like…well…dropping. Anytime you transport a medium from one location to another physically you put that data at risk.
Just my .02 cents.