Ask Slashdot: Personal Tape Drive NAS?

New submitter hey_popey writes "I would like to piggyback on a previous Ask Slashdot question. Do you know of any realistic way to use a tape drive solution at home, not as a backup, but as a regular NAS? I would like, for example, to save the torrents of my Linux distributions on it, and at the same time, play the family videos on a computer. It would seem at a first glance that the transfer rates and capacity of Linear Tape-Open (1.5TB, 280MB/s in 2010) and the functionality of LTFS would allow me to do that, but I don't know the details, or whether this would be economically viable."

Comments

Nope.

[Sprite_tm]

The big disadvantage of tapes is that it has long seek times. Not 'long' as in a few times that of a hard disk, but 'long' as in: can take a full minute to do. Access of multiple files on a normal HD is done by reading a meg of the first file, then seeking to the second file and reading a meg, going back to the first file and reading a meg etc. On a tape drive, even when the seek time is only, say, 10 seconds, you'd get a total throughput of 100K/sec that way. And I'm not even talking about the havoc that using it for storage of torrent files wreaks on it: that's a random-access process if I ever saw one, and the seek times on tape would kill your bandwidth very quickly, and probably your tapes too (because of wear&tear).

Re:Nope.

[DeathToBill]

I'm not sure you've got the point. Images of Linux distros are big, contiguous files that you want to access rarely and read linearly - probably just the thing to go on tape. To a certain degree, video is the same - one big file that you want to read linearly.

Of course, the practicalities might not be so great. If you want to share the torrent back with the community, then that's a problem. So is wanting to skip around in a video.

But I don't think the question is quite as insane as you make out.

Re:Nope.

[Sprite_tm]

For playing a movie - maybe. For actually burning a torrent - fair enough... if that is the _only_ thing that happens.

The point is that multiple accesses is going to delay the drive by a huge amount. If you want to, say, copy that Linux iso to your NAS at the same time as someone is playing a movie, the tape drive is going to have to move between the locations of the two files, which is going to wreck the access times, as I stated. Torrents are worse: you're downloading from / uploading to a bunch of other computers, all wanting to read from or write to a different location in the file. Again, this means moving between locations and the resulting huge access times.

You may be able to alleviate the process by putting a SSD or HD as cache in between, but I'm not sure if there's off-the-shelf software to do that, and I'm not even sure if that's going to work comfortably. Besides, if you're going to put a SSD or HD in between, why not just use that?

Re:Nope.

[Lumpy]

Yup a lot of people don't remember linear access. and a minute or two? I remember a 15 minute seek and load time when restoring a file from the end of an archive tape.

In fact it's faster to download a new distro on a 7mbps DSL line than it is to find it on the tape.

Now, I have seen with a tape robot cabinet a "infinite" hard drive. 4 hard drives for online storage, they had 4 hard drives for nearline storage, and all the tapes in the cabinet for offline storage. if you accessed the file from online and it was on tape, you would get a winpopup from the server stating that the file is in offline storage and will be spooled up for you. it then would email the person when the file was put back into nearline or online storage storage.

back in 2002 it was how we had 22Tb of tv commercials, Tv show productions, and video footage available for the video editing suites.

Re:Nope.

[fuzzyfuzzyfungus]

and probably your tapes too (because of wear&tear)

the hideous, desperate seeking of a tape in this condition is informally described as 'shoe-shining'...

Re:Nope.

[sortius_nod]

I only live with my partner & there's many circumstances where I'm copying to/from my server while she's watching a video & vice versa. Then there's downloading a torrent on the server while both of us are accessing it. Even if it's one person, if you're watching a movie & even refresh the directory listing your movie would stop. This is probably the worst "Ask Slashdot" I've ever seen.

Written by someone with no grasp of technology & approved by someone with even less of a grasp on reality.

Re:Nope.

[Joce640k]

1) Fast
2) Cheap
3) Large capacity.

Pick two.

Re:Nope.

[circletimessquare]

"Written by someone with no grasp of technology"

Your comment written by someone with no grasp of the history of technology. There's folks reading your words who remember reading and storing files from cassette tapes in the 1980s. Like me.

"approved by someone with even less of a grasp on reality"

Story approved by someone with an appreciation that the geekiest novel solutions to problems are things unimaginative people would never consider seriously until forced to, because everyone else is enthusing about how cool it is. Let your mind wander into crazy scenarios and impossible what-ifs. Or butt out. Because some people come to Slashdot for exactly this talk on just this topic of the way-out-there.

"Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway." - Andrew Tanenbaum, 1996, Computer Network

Re:Nope.

[Nutria]

"Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway." - Andrew Tanenbaum, 1996, Computer Network

You're missing the point that tapes are sequential devices. Forcing random access onto them plunges (a) latency and throughput, and (b) the life of the tape.

This is a completely wrong usage for tapes.

Re:Nope.

[iamgnat]

"Written by someone with no grasp of technology"

Your comment written by someone with no grasp of the history of technology. There's folks reading your words who remember reading and storing files from cassette tapes in the 1980s. Like me.

I too used tape drives in the 80s, but my grass is not remotely brown enough and my glasses are not tinted nearly enough to begin to think of those as "the good old days" when thinking about storage solutions. I agree with the GP that this question was asked by someone that doesn't have any clue what the linear nature of a tape means and has never been stuck waiting on a restore of a file that happens to be at the opposite end of the tape than the current position.

I would agree with you about "novel solutions" if the question had instead been about how to use a disk and tape combination similar to RAM/swap and age out files with low access rates to tape while keeping the most used stuff on the faster disk or something else equally "out of the box". In this case it is just someone trying to use an exceptionally wrong tool for the wrong job and there is nothing novel about it (unless we are talking about the stupidity of it).

Also, Andrew was talking about transferring large amounts of data between sites in the days when the Internet was slow, HDDs weren't a good/stable transport method, and cross-site replication was expensive and limited in scope. He was not remotely referring to using tapes to solve an inherently random/multi access problem, so while it is still a funny quote it isn't relevant to the discussion at hand.

Re:Nope.

[UnknowingFool]

l

Of course, the practicalities might not be so great. If you want to share the torrent back with the community, then that's a problem. So is wanting to skip around in a video.

But I don't think the question is quite as insane as you make out.

Forgetting about or not thinking about the impracticalities is the insane part. I can hammer nails with my shoe but asking on a home improvement or shoe site the best way to reinforce my shoes so I can use them to build a tree house is pretty insane.

Re:Nope.

[fche]

"Never underestimate the bandwidth of a station wagon ..."

And never underestimate the latency either.

Re:Nope.

[mlts]

I still use tapes today, and I think they would be nice for home use since I can pick up LTO-3 tapes for about $15 a pop, and LTO-5 tapes for around $42 each.

However, if one thinks a tape can be a random access device, they need to think again. Tapes are great for making sure data is copied somewhere safely, and once the read/write switch is flipped, that the data stays safe.

My recommendation: Keep the tape drive for backups, but go with two mirrored drives, or some other RAID configuration (other than RAID 0) to minimize the impact of a HDD failure.

Re:Nope.

[operagost]

The station wagon analogy is an amusing analogy to bring up, because if you're willing to wait for videos to stream off of tape, why not just use your station wagon to go to a video store or Redbox?

Re:Nope.

[carnivore302]

for the love of god, buy a regular NAS

Re:Nope.

[TheRaven64]

I still use tapes today, and I think they would be nice for home use since I can pick up LTO-3 tapes for about $15 a pop, and LTO-5 tapes for around $42 each.

Not really home user price. LTO-3 is 400GB, LTO-5 is 1.5TB. At that sort of capacity, a home user is unlikely to need more than a handful of tapes. With LTO-5, three tapes would be enough for most home users with fairly aggressive backup strategy: two off-site, one being rewritten. If you're only buying three tapes, the cost of the drives becomes very important. The cheapest LTO-5 drives I can find cost over $1,000. At that price, you may as well just buy three 1.5TB hard drives and save the money. Tape is only really cost effective for situations where you have a lot of tapes.

Re:Nope.

[tibit]

All I remember is that my tape adventure ended with an LTO-3 drive that lasted about a year, doing daily backups, on a 7 tape daily rotation. I had two LTO/DLT generations before that, and a prior helical scan system with smaller tapes as well. The Linux kernel drivers for tape devices never worked all that well -- getting good throughput required tweaking and I had to add a large buffer between gzip and tape in spite of a fast machine. The particular drive in question worked fine on RHEL4 but would not work on a Dell server under RHEL5 where the throughput went to hell -- it was 5-8x slower. If you plan on using any tape drives, make sure that you test the exact combination of server, interface, interconnect, drive, tape, Linux distribution and backup software/scripts you're going to run it as. Anything less may lull you into a false sense of accomplishment that will be blown away in short order once it fails in production.

In times of linux kernel 2.0 I had some junk machines that had ISA-based Adaptec SCSI cards and worked quite well with old 80 megabyte aluminum-plate-backed tape cartridges. It was slow, but it still kept the tape streaming at full speed. It was foolproof, and redirecting tar -z output to /dev/st0 was all that was needed to get it to work, after setting desired block size. Even on a 486-class machine. It seems that it was downhill ever since in terms of ability for the systems to maintain streaming and retain data. I can still read those 80 megabyte tapes with zero errors. All of a dozen of them or so. All of the newer tapes would develop errors under normal use, sometimes after a couple of uses!

Re:Nope.

[repvik]

This is what so many people seem to fail to understand. Tapes are still very useful. They, however, serve a completely different use case.

Yes. Enterprise backup with bucketloads of tapes. For Joe Home User, a couple of 2TB drives in enclosures would be very much cheaper, just as fast/faster, and about as easy to take offsite (which in my experience, never happens with home users).

begone rational thought

[Anonymous Coward]

you're not thinking this through, are you? it's a tape-drive...

Re:begone rational thought

[Anonymous Coward]

Leave him alone! help me with my RAIF - Redundant Array of Independent Floppies

You cannot

[Anonymous Coward]

No. Just no.

Re:You cannot

[Tx]

Forget LTO, I recommend a massive array of Sinclair Microdrives. I mean, if you're going for a silly and impractical tape solution, you might as well push the boat out.

Re:You cannot

[CastrTroy]

I really don't know what the editors were thinking when they posted this. There is no constructive conversation that can come from this question. Perhaps it should be migrated to SuperUser

need cache drive in front

[gl4ss]

you'd need a cache drive in front of it.

the mb/s is ok yes, but that's for linear read/write from the tape.

"While specifications vary somewhat between different drives, a typical LTO-3 drive will have a maximum rewind time of about 80 seconds and an average access time (from beginning of tape) of about 50 seconds.[21][dead link] Note that due to the serpentine writing, rewinding often takes less time than the maximum."

the tape is also only good for 260 full passes.

just buy a hd based nas, archive to tape if you really archive that much stuff. but load it on hd first for gods sake.

Re:Seek Time

[Anonymous Coward]

I agree that a tape solution would not work well for torrent files, however using it to store movies should work well. If you wish to market it, I can suggest a name for it. You could call it a VCR. But whenever you do, do not call it Betamax, I don't think that would sell very well.

Harddisk cache

[mwvdlee]

Unless you stuff a large harddisk inbetween as cache, I don't see how you can make this perform anywhere near bearable.
Note that frequent write/delete cycles will fragment tape space like you wouldn't believe (perhaps a weekly tape reorganization job would be in order?).
I used to work on z/OS where using tape for normal storage isn't unheard of; typically files not accessed for a while are moved to a tape robot.
When trying accessing one of those files, it did so by writing the file back to harddisk for actual access.

Cost vs HDD Solution

[thesandbender]

The overwhelming issues with latency aside, a 1.5TB (native not compressed) LTO drive will set you back ~1800 USD and you'll need an extra ~100-150 for a SAS controller that can drive it. For that price you can by yourself 24TB of HDD storage (12 x 2TB) with enough money left over for a decent SATA/SAS RAID controller. If you setup a RAID 10 array you'll have 12TB exponentially faster access times and better data security (unless you make copies of every tape).

Re:Cost vs HDD Solution

[dtdmrr]

Note that the 1800 is just for the tape drive. An 8 tape library with drive and media will be more like $4k, and that still only gets you 12TB (given the file types you mentioned, don't plan on getting any capacity boost from the LTO compression). You will have to go with one really big library before tapes win on price. Unless of course you are willing to change tapes manually, or build your own robot/library out of lego. But even then that 24TB figure is only a lower bound on the cross over.

Re:Cost vs HDD Solution

[Kvan]

Several reasons:

• Economies of scale do win out for tape once you start hitting hundreds of TBs.
• Tapes are easy to move offsite.
• Tapes don't consume any power when not in use.
• Tapes are much more resilient than hard drives against environmental factors (mechanical, temperature etc.)

The last point in particular is why you don't see HDD robots: all that handling would skyrocket the hard drives' failure rate.

Re:Cost vs HDD Solution

[thesandbender]

It's economies of scale, tape has a high cost of entry but a relatively low maintenance cost. A 1.5TB LTO 5 tape costs 40 USD. A 1.5TB drive costs 90 USD. The VM enclave I use for testing at one client has 700TB, to back up that data set with HDD would cost 23,333 USD more than tape (for just the media). That difference alone covers the cost of a tape library. And, most corporations are going to take complete backups once a week with incremental backups during the week. Which means an extra 23,333 a week (HDD vs tape). Scale this out to petabytes of data and HDD's become prohibitively expensive.

Also, one of the primary reasons to use tape is you can store them offsite for disaster recovery. You can put a box full of tapes in the back of a panel van and drive them down a bumpy gravel road without any big worries, you just can't do that with HDD's with out protective housing.

Punch cards

[Billly Gates]

Have you considered punch cards? You can get a vintange IBM 370 for only a few hundred thousand and a warehouse to store all the punch cards for just several million. Put it in China and you can have a few servants ravage up with forklifts and storage boxes with the cards and scramble to put them in the reader and upload it back to your home media server.

I mean who cares about using a cheap $200 external usb drive like everyone else pretending we somehow live in the 21st century ... pfft

Tapes. Are. Useless.

[fraxinus-tree]

They are not only useless at home. They are completely useless as a backup solution in the first place. They refuse to read in 95% of their intended usage scenarios, including, but not limited to, incompatible/failed tape drives, missing/obsolete/buggy/outright stupid software, degraded/stretched/torn off tape, mislabeled/misordered media and so on. And then again, they cost $$$$$, because PHB's keep on buying them. And they do, because they like solid-looking stacks of backups. Even if no one prescribing them in the backup plans had ever tried to restore a single file in the last 20 years. Or ever.

Hard disks are good. They are also good for backups. They are cheap, they sell them in the shop down the street, they work 99.99% of their intended usage scenarios, do very well in every other usage scenario, and they can be easily connected to any computer, just to see what's in.

Re:Tapes. Are. Useless.

[Anonymous Coward]

They refuse to read in 95% of their intended usage scenarios, including, but not limited to, incompatible/failed tape drives, missing/obsolete/buggy/outright stupid software, degraded/stretched/torn off tape, mislabeled/misordered media and so on. And then again, they cost $$$$$, because PHB's keep on buying them. And they do, because they like solid-looking stacks of backups. Even if no one prescribing them in the backup plans had ever tried to restore a single file in the last 20 years. Or ever.

Being an enterprise backup engineer, I have to disagree with the bulk of this. We do thousands of tape restores every year, the tape media is extremely reliable, and modern tape is FAAAST. Nothing can do streaming database backups or restores faster than tape, particularly multithreaded - at that point, most servers and network infrastructures don't have enough throughput to keep up with the tape drives.

Now, Joe Admin at an SMB with hand-labelled tapes (versus barcoded), poorly managed and mismatched tape drives, and poorly planned and tested emergency recovery scenarios is a problem.... but that just means that the person making the technical and purchasing decisions doesn't know how to take advantage of tape properly. If you've got mismatched tape hardware versions, tape drive firmware versions, software problems, etc - well, that's a problem of the person managing the solution. Like any other technical solution, if you're poorly trained on backup solutions, you're going to have a poor implementation. You reap what you sow.

Disk backup has its place, certainly (and my company leverages it heavily as well), but don't write off tape as useless or a poor technical solution. If you need a database backup restored with the smallest RTO, nothing does it faster than tape.

A long long time ago in an OS far far away...

[wisebabo]

... there used to be a product called "Desktape" made by a company called Optima Software.

Basically it kept a cached (on the system drive) directory listing of all the files on the tape, and then made a (virtual) disk using that directory which was mounted on the desktop (hence the name). The user would perform file transfers with this "disk" in much the same way as he would a real disk, he could copy files to and from it by dragging and dropping, similarly erasing or copying over files. Note that I said file transfers; direct random access to this "disk", while possible, were strongly recommended against because the tape would seek to one block, then seek to the next etc. so, for example, launching an application from the tape was ill-advised. Anyway, when the tape was ejected, the directory would be updated on the tape.

Still it was great because it made backing up very simple (no special utility to run) and this disk would behave just like a real disk so that you could run regular disk utilities on it like "Virtual Disk" (which kept searchable online copies of directory listings of offline volumes).

The software was hardware agnostic which means it could work with a variety of tape drives so maybe it would work with LTO. Alas, the software only ran on pre-OS X Macintoshes and the company is long gone. I would dearly love it if someone could revive this software and make it work with a "modern" OS! Can't someone buy the IP of this company?, surely the development (patents?) is worth something. (I wish there was some sort of law saying that abandoned software like this would, after 5 years, be put in the public domain; of course for this to work the source code would have to be continually archived at, say, the Library of Congress in case of sudden bankruptcy. Not too feasible.)

More brilliant ways to re-purpose random stuff

[Rob_Bryerton]

Did you know you can refrigerate your food by placing it in front of your air-conditioner?
And who needs a stove or oven? Simply wrap your food in your discarded tinfoil hats, and place it on your engine block; by the time you get to the office, breakfast will be ready.
I've also heard you can pound nails with a screwdriver if you adjust your grip...

As a co-worker of mine is fond of saying: "There are no stupid questions. Except for that one..."

While it's a dumb idea, it's been done

[jtownatpunk.net]

Back in the before time, I knew a guy who ran a BBS who came about a DAT drive by some method or another. I assume he stole it from work. Anywho, that was a lot of storage back then and he wanted to use it to store files for the BBS. What he came up with was a caching system where people tagged the files they wanted, the files would be copied from tape to temp storage on the hard drive, would be downloaded by the user, then deleted from the hard drive. I had a similar system for the CD-ROM changer on my multi-line BBS. If someone on line 3 wanted file from Disc_2 and someone on line 1 wanted a file from Disc_7, the poor thing would just thrash back and forth between discs until I added the caching system.

But it's just totally impractical today. I've got a 26tb array for my bulk storage. Even with hard drive prices still a bit inflated, it could be built for $2500 with nice drive cages. $3200 for 39tb using 3tb drives.

An LTO 5 library is going to run you $5000 for just the drive/library. You weren't going to stand there swapping tapes by hand, were you? Another $550ish to fill it with tapes. And that's only 1.5tb gigs per cartridge. (Native capacity is what you should be using for this type of data.) 16*1.5=24tb online for around $5500. Nevermind the cost of the caching system that would be needed just to make it work in even the most crude manner with a minimum of 5 minutes between initial request and the file being available for use. More than double if it spans tapes.

So roughly double the cost for a similar amount of storage with horrendous access times. Sounds like a plan. You should totally do it and report back.