In the previous article, I covered the first five of ten reasons why tape is still important. Now, let’s consider the other five reasons.
6. Tape is greener for storage
Offline storage of tape is cheap, from an environmental perspective. Depending on your locality, you may not even have to keep the storage area air-conditioned.
Disk arrays and replicated backup server clusters don’t really have the notion of offline options. Even if they’re using MAID, the power consumption for the psuedo-offline part of the storage will be higher than that for unpowered, inactive tape.
7. Replicated tape is cheaper than replicated disk
And by “replicated tape” I mean cloning. Having clones of your tapes is a cheaper option than running a system with full replication. Full replication requires similar hardware configurations on both sides of the replica; cloning a tape requires – another tape. That’s a lot cheaper, before you even look at any link costs.
8. Done right, tapes are the best form of thin provisioning you’ll get
Thin provisioning is big, since it’s an inherent part of the “cloud” meme at the moment. Time your purchases correctly and tape will be the best form of thin provisioning within your enterprise environment.
9. Tape is more fault tolerant than an array
Oh, I know you’ve got the chuckles now, and you think I’ve gone nuts. Arrays are highly fault tolerant – looking at RAID alone, if your disk backup environment is a suite of RAID-6 LUNs, then for each LUN you can withstand two disk failures. But let’s look at longer term backups – those files that you’ve backed up multiple times. Some would argue that these shouldn’t be backed up multiple times, but that’s an argument that doesn’t translate well down into the smaller enterprises and corporates. Sure, big and rich companies can afford deduplicated archiving solutions, but smaller companies have to make do with the traditional weekly fulls kept for 5 or 6 weeks, and monthly fulls kept for anywhere between 1 and 10 years will have the luxury of a potentially large number of copies of any individual file. The net result? Perhaps as much as 50% of longer term recoveries will be extremely fault tolerant – if the March tape fails, go back to the February tape, or the January tape, or the December tape, etc. This isn’t something you really want to rely on, but it’s always worth keeping in mind regardless.
10. Tape is ideally suited for lesser RTO/RPOs
Sure if you have RTOs and RPOs that demand near instant recovery with minimum data loss, you’re going to need disk. But when we look at the cheapness of tape, and practically all of the other items we’ve discussed, the cost of deploying a disk backup system to meet non-urgent RPOs and RTOs seems at best a case of severe overkill.
Hi Preston.
This is interesting, and after reading your explanations, it’s obvious.
May I propose a topic for you to blog about? I’d love to get your opinion on this, as I’m sure many other also.
What is your perspective on looong term retention for personal and business data?
E.g. my precious pictures that makes up many many GB already. What’s the best way to protect them digitally so I’ll be able to browse them in 30 years? Mozy? CD ROM, HD, tape?
A friend of mine says that this first decade of the 21st century is the most photographed in human history. But in 50 years, we might have a gap in number of pictures of that decade compared to the 50 years before.
Sincerely,
Johannes
This is one of those complex discussions, but the most important point is to look at business requirements (RTO/RPO against value of lost business) and TCO (including operational costs).
You are correct that de-dupe is for the big boys, becaus ethe software companies see it as the latest revenue generating mechanism, thus pricing it beyond the SME. However, like all things, it will move down market and become cost effective to teh SME market over time.
So, when you use de-dupe you do find that the amount of data you can store per $ starts coming much closer to tape. No matter what you do, though, you shoudl always have 2 copies. If you have only one copy on tape, you are risking data recovery. If you have only one copy on disk, and don’t do a tape copy, you are risking your company for DR. What you should do with disk is replicate it to off-site… if you can afford the bandwidth… again de-dupe helps.
operational cost is very important. We find that we can backup 4 times as much data, using disk based backup devices, per backup admin as compare dto tape. Mainly this is because the disk based devices are more reliable (higher MTBF). tape is still used, but it is not so critical when it fails as it is now more of an archiving medium rather than a backup medium.
to give you an idea on MTBF, we don’t ahve a single LTO drive that is out of warranty – because they break down so often, that they get replaced before warranty is up.
As for greener, look at spin-down technology. Still not as good as tape, but certainly helps. then, if you are doing off-siting, what’s the carbon foot print of the guy showing up, running his engine, and then taking your tape to somewhere else?
I don’t think, for aminute, that tape will be dead for a long time… but watch out for memory devices! The price is coming down and expected to get cheaper than disk!
Hi Preston,
I couldn’t agree more, especially on number 9: you would be surprised (or, uhm, probably not, come to think of it 🙂 ) how many (firmware related) problems I’ve seen with VTLs from a certain big manufacturer, leading to data loss possibilities most people wouldn’t imagine.
Hi Alex,
I’ve not yet encountered a single VTL that I entirely liked. Yes, I recognise the need for them, but none of them seem as reliable as they should be. I.e., for something with no tapes/tape drives, they still seem to periodically manifest tape-like errors such as media becoming stuck, etc.
Cheers,
Preston.
Hi Preston,
I completely agree with point 8 and I think it is something that is often overlooked. I do think, however, that tape thin provisioning extends beyond simply timing your purchases correctly and, instead, can be enabled through the intelligent and just-in-time allocation of tape media to applications that would seek to use it as I explore here (http://blog.greshamstorage.com/tape-thin-provisioning/). What are your thoughts?
Cheers,
Chris