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Data Storage

How Do You Backup 20TB of Data? 983

Sean0michael writes "Recently I had a friend lose their entire electronic collection of music and movies by erasing a RAID array on their home server. He had 20TB of data on his rack at home that had survived a dozen hard drive failures over the years. But he didn't have a good way to backup that much data, so he never took one. Now he wishes he had.

Asking around among our tech-savvy friends though, no one has a good answer to the question, 'how would you backup 20TB of data?'. It's not like you could just plug in an external drive, and using any cloud service would be terribly expensive. Blu-Ray discs can hold a lot of data, but that's a lot of time (and money) spent burning discs that you likely will never need. Tape drives are another possibility, but are they right for this kind of problem? I don' t know. There might be something else out there, but I still have no feasible solution.

So I ask fellow slashdotters: for a home user, how do you backup 20TB of Data?"
Even Amazon Glacier is pretty pricey for that much data.
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How Do You Backup 20TB of Data?

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  • Crashplan (Score:5, Informative)

    by rossjudson ( 97786 ) on Wednesday March 12, 2014 @09:34AM (#46462849) Homepage

    Crashplan has unlimited storage. I use their home plan; it's unlimited for up to 10 machines. I think I am backing up about 6TB there now.

  • by DogDude ( 805747 ) on Wednesday March 12, 2014 @09:35AM (#46462863)
    I have a 16 TB media collection at home that I just back up on more hard drives.

    External hard drives in USB cases + Robocopy works great for me.
  • Re:reduce the amount (Score:4, Informative)

    by buchner.johannes ( 1139593 ) on Wednesday March 12, 2014 @09:40AM (#46462977) Homepage Journal

    20TB is not out of the world. With a RAID of 4TB disks you can cover that at home, and it doesn't need to be on all the time. Maybe you can reduce the amount of disk usage by reducing duplicate content using bup [github.com] or an appropriate FS.

  • Good luck. (Score:4, Informative)

    by TheCarp ( 96830 ) <sjc@carpane3.14t.net minus pi> on Wednesday March 12, 2014 @09:41AM (#46462985) Homepage

    A quick check at one service which lists such large amounts, you would be looking at almost $20k/year to keep a single offsite copy of that. That is the posted price however, I imagine that is enough that you could shop around and find a deal, but, a deal is still going to be prohibitive for most people.

    At 20 TB I would start thinking about one of two things: Tape, and/or git-annex.

    Unless prices have changed since I last looked and the scales tipped, tape has the advantage of being cheap. Of course, you will need to test your tapes occasionally and likely want 2 copies just in case, but, at that point you are invested in tape, may as well.

    The other possibility is git-annex and lots of drives, but you can mix types. That way you can keep a catalog of your library and information on where it all is, and how many copies of each thing you have.

    Of course, any way you slice it, each physical piece of media is something that can fail so you have to occasionally test to ensure redundancy.

  • I agree but... (Score:5, Informative)

    by Matteo De Felice ( 3574477 ) on Wednesday March 12, 2014 @09:53AM (#46463155)
    I agree, I've been using Crashplan for three years and the unlimited space it's really great BUT... ...I'm not sure about the bandwidth they provide: how long it will take to upload 20 TB? Anyway, I don't see what's the problem in using external drives for backup. Here in my lab I've realized that the best way to backup X Terabytes is to have another storage with X Terabytes...
  • by stoploss ( 2842505 ) on Wednesday March 12, 2014 @09:58AM (#46463223)

    These "unlimited" claims always turn out to be lies. When will we learn?

    My friend paid for an "unlimited" account from JustCloud for backup. He stored 1.8 TB on it and then they "fair use"'d his ass and canceled his account. They didn't even give him a refund for the rest of the money he prepaid.

  • by jeffmeden ( 135043 ) on Wednesday March 12, 2014 @10:05AM (#46463307) Homepage Journal

    Glacier at $20 per month for 20TB is rediculously cheap by today's standards. And at those sizes, you'd want to ship those drives to Amazon instead of uploading. We do this all the time and it's not that hard.

    The price of TBs of storage of course will come down without question. But by today's standards $20/month for a medium that won't "bit rot" on you is an amazing deal.

    You missed a 0, he has 20,000GB and the cost for glacier is $.01/gb/mo (not including upload charges). So, Glacier would cost him $200 a month or $2400 a year. Not hugely expensive but if you are OK with a quasi-local copy (offline and stored in a fire safe, perhaps) you could do it cheaper for less, after you hit the 1 year mark.

  • by Anonymous Coward on Wednesday March 12, 2014 @10:05AM (#46463315)

    No one will ever see this anonymous post but a cheap robot changer (used) on ebay can be had from between a few hundred to a few thousand dollars. Most of us are geeks and love technology. I use two such devices, couldn't imagine life without them. LTO4 is still the sweet spot in storage cost (media) and capacity. The tapes hold 800GB and can be purchased for around $22 dollars each.


  • Re:Hmmm... (Score:5, Informative)

    by Cassini2 ( 956052 ) on Wednesday March 12, 2014 @10:10AM (#46463387)

    At 10 characters per second, the backup would take 63,419 years(*) and require 659 TJ or 0.2 TWh of power to complete. I have a customer that still uses paper tape. It lasts and lasts, and I have only replaced the reader once. The punch needs a new power supply every 20 years or so.

    However, 63,419 years is a long time to wait for a backup to complete.

    (*) this assumes that 1 TB = 1,000,000,000,000 bytes. It takes almost 70,000 years if you add the extra 10%.

  • Re:Hmmm... (Score:4, Informative)

    by Thanshin ( 1188877 ) on Wednesday March 12, 2014 @10:11AM (#46463393)

    20TB = 1.33LoC

  • Re:Hmmm... (Score:5, Informative)

    by Lumpy ( 12016 ) on Wednesday March 12, 2014 @10:14AM (#46463443) Homepage

    Punch the hole and you can flip them over to double your capacity.

  • Re:reduce the amount (Score:4, Informative)

    by FreonTrip ( 694097 ) <(moc.liamg) (ta) (pirtnoerf)> on Wednesday March 12, 2014 @10:16AM (#46463471)
    I'd switch to x264 in an MKV container - you can get the same quality in about 3/4ths the file size without even being clever.
  • Re:Hmmm... (Score:4, Informative)

    by Chrisq ( 894406 ) on Wednesday March 12, 2014 @10:18AM (#46463489)
    According to this site [onlineconversion.com] 2560 Meters = 1 Meg. So that would be 20,000,000 times 2560 = 51,200,000,000 metres = about a third of the way to the sun
  • Re:Hmmm... (Score:4, Informative)

    by Old97 ( 1341297 ) on Wednesday March 12, 2014 @11:37AM (#46464457)
    The first 8" I used held 128k. The last one had a capacity of around 1.2 mb. They were twice as fast (transfer rate) as those new fangled 5 1/4 inch floppies. Kids, what do they know?
  • Re:Hmmm... (Score:5, Informative)

    by idontgno ( 624372 ) on Wednesday March 12, 2014 @11:52AM (#46464639) Journal

    At the very end of the 5 1/4" floppy era, the "High-Density" floppy used the same data rate, tracking, and recording density as the 8" 1.2M floppies. They were, in fact, 1.2M 5 1/4" floppies. Which is why their formatted capacity was different from 3.5" "high-density" equivalent, 1.44M.

    Other than electrical needs (as 8" floppies often had their spindle motors directly powered by 120VAC line current), the high-density 5 1/4"s were used as a drop-in replacement for 8" floppies in the hobbyist retrocomputing community. (Not collectors, though; they'd want to keep the gear as cherry as possible.)

  • by ewilts ( 121990 ) on Wednesday March 12, 2014 @12:32PM (#46465115) Homepage

    The dataset isn't that huge. Tape can write at speed at least as fast as disk - LTO-5 writes at up to 280MB/sec - far faster than you can read the source at which isn't likely to be fast disk. The seek for a single-file restore will be slower than disk but after the initial seek, the read will be as fast as from a typical archive disk (no, you're not archiving 20TB to SSD, nor are you storing the source data on SSD either)

    However, the change rate for this application is likely to be low. That makes it very feasible to do random testing from the new backups where a minute to do the tape mount/seek is not a problem. You won't be writing more than a single tape in any single run (LTO-5 is ~1.5 TB of uncompressed data).

    For $2K, you'll have the LTO-5 drive. Add $500 for 20 tapes and you can back up the entire set (once) plus a bunch of incrementals. I haven't done the math with LTO-6 which is faster and holds more data. If you want multiple generations, tape is a lot cheaper per TB than disk. The initial drive cost hurts but after that, the price is good at $15/TB or so.

  • by ewilts ( 121990 ) on Wednesday March 12, 2014 @12:38PM (#46465185) Homepage

    You're dating yourself. LTO-5 is 1.5TB native, 3TB compressed at $25 per tape. LTO-6 is 2.5TB native and 6.25TB compressed. Both of those compressed numbers are using the built-in compression in the drive.

    A 10-pack of LTO-5 tapes is about $250.

    You can easily encrypt the tapes and tape them offsite. You can keep a copy onsite and offsite. You're simply not doing that with disk.

    Your speed is also off - an LTO-5 can write at 280MB/sec. The limiting factor is not the write time on the media but the read time from disk.

    Restore times are typically limited by the write rate on the destination raidset, not the read rate from tape.

  • by grumbel ( 592662 ) <grumbel+slashdot@gmail.com> on Wednesday March 12, 2014 @12:38PM (#46465191) Homepage

    LTO-6 can hold 2.5TB per tape, a tape cost ~$70, the drives cost $2000. That's still more expensive then just more HDDs for 20TB, but at >50TB it might be worth it.

  • by afidel ( 530433 ) on Wednesday March 12, 2014 @12:50PM (#46465305)

    You can find a bunch of SAS LTO4 drives on ebay for ~$50-75, and adding a SAS PCIe HBA doesn't cost much more (if you have 20TB I assume you already have a tower).

  • Re:Hmmm... (Score:4, Informative)

    by lgw ( 121541 ) on Wednesday March 12, 2014 @01:30PM (#46465733) Journal

    Tape drives need the full SCSI command set, not the trimmed version that made it in to SATA (I'm not sure there's even a "(01) REWIND" supported in SATA).

    LTO tapes stored reasonably ("keep in in a cool dry place", as the song goes) should last 15 years from any vendor, as that's in the spec, and there aren't really bottom-feeder vendors for LTO.

  • Re:reduce the amount (Score:5, Informative)

    by wagnerrp ( 1305589 ) on Wednesday March 12, 2014 @01:44PM (#46465967)

    The problem with RAID-5 is that you are 2 disks away from failure and rebuilds often kill the disks.

    No. The problem with RAID-5 is that during a rebuild, there is a reasonably possible chance you could have a UBE, and lose one bit, making perfect recovery of the array impossible. Only a stupid controller would consider a UBE to be a failed drive and trash the entire array. On RAID-6, you still have the same possibility of a UBE, but the chances that two separate drives would experience one on the same exact block during a rebuild are so astronomically slim as to be irrelevant.

I was playing poker the other night... with Tarot cards. I got a full house and 4 people died. -- Steven Wright