[Pc_Support] Re: Tape drive for small file server .... -- LTO (unless you have existing AIT or DLT assets)

[Bryan J. Smith]

[ Since this is a cross-post, don't forget to remove the list prefixes
before you respond ]

On Sat, 2006-06-17 at 10:59 -0500, William A. Mahaffey III wrote:
> .... I am in the market for a tape drive for my smallish file server on 
> my LAN.

Is this home or work?  I assume work?

BTW, I don't know if I posted this in another thread before, but I
really tried to talk about backup strategies -- on-line, off-line,
remote, near-line, etc... -- and the inevitable evolution of the
near-line (e.g., managed disk) + off-line (e.g., tape cartridge) into
the "Virtual Tape Library" (although that's more for enterprise
networks) in my 2005 September Sys Admin article:  
  "Dissecting Virtual Tape Libraries"  
  http://www.samag.com/documents/sam0509a/  

People argue disk and take back and forth and there are
advantages/disadvantages to each -- and they really complement each
other today.  In your case, probably not much, because I assume you're
only backing up a single server and not other systems over the network.
But I still want to point it out.  It's really _not_ about "disk v.
tape" but "where does disk fit in?" and "where does tape fit in?"

The only time I've seen people argue otherwise is when they are doing
bonehead things like backing up over the network in real-time.  They
argue backup window when you should _never_ use tape over the network,
but near-line disk as at least an intermediate store, to address the
backup window.  Otherwise, such thinking is 1980s-era.

> The box is an i865 (yuk !!!) P4, 2.4 GHz, 2 GB RAM, SuSE 9.2, 
> box-stock (no recompiled kernels, no YAST updates, straight off the 
> ROM).  It has a 20 GB root drive, a 200 GB /home drive, & a 400 GB drive 
> mounted as /work, all EIDE. I would like to backup parts of the /home & 
> /work for offline storage.

You should also consider near-line storage -- something that would not
only let you recover data faster, but diff/buffer backups before they go
to tape.

Now for a single server, that's probably not as big of a deal.  But as
you start backing up more and more of your network, it's a good idea to
have a few TBs of disk for "near-line" and then a tape cartridge that
holds at least what a weeks worth of "critical, longer-term off-line." 

> I have poked around on NewEgg & observe 2 apparently contemporary
> options, Sony AIT-1/2

Yes, Sony's 8mm format.  Unless you have existing AIT assets, I
recommend LTO instead.  LTO is more reliable, faster and has the lowest
price per GB -- drive and media.

Same deal for HP/Quantum 1" DLT.  Unless you have existing DLT assets, I
recommend LTO instead.  LTO isn't any more reliable than DLT (only IBM's
proprietary format is more reliable), but it's faster and has the lowest
price per GB -- again, drive and media.

> & something called Ultrium1/2 or LTO-1/2/3 or LTX100/200G,
> all apparently used interchangably except for version #'s. 

LTO (Linear Tape Open) began as a triple vendor standard -- HP, IBM and
Tandberg (IIRC).  It is now supported by almost a dozen firms, with half
of them making drives.  The popularity has driven _commodity_ cost and
LTO will be around for a _long_time_ -- and 10-15 years** from now,
you'll still be able to get a LTO-4 drive so you can read _all_ of your
LTO-1/2/3/4 tapes.  http://www.lto.org/

**NOTE:  LTO, like DLT, is probably the most reliable, longest lasting
"commodity" backup cartridge you can get.  Only IBM's proprietary
solutions (slower, less capacity, very costly) last longer (25+ years).

HP calls their drives Ultrium and they are rated by a model in GBs that
matches a 2.4:1 ratio.  E.g., the LTO-3 drive (400GB native, 80MBps DTR)
from HP is Ultrium 960 (960GB assuming 2.4:1 compression, 192MBps
effective DTR).

LTO has 3 current (LTO-1, 2 and 3) and 1 (LTO-4) planned standard:  
  LTO-1    100GB, 20MBps DTR native -> 240GB, 48MBps DTR 2.4:1
  LTO-2    200GB, 40MBps DTR native -> 480GB, 96MBps DTR 2.4:1
  LTO-3    400GB, 80MBps DTR native -> 960GB, 192MBps DTR 2.4:1 
  LTO-4*   800GB, 160MBps DTR native -> 1.92TB, 384MBps DTR 2.4:1
*Planned (since day 1), which should be the last

LTO-1 drives are under $1,000, possibly as low as $500 used/refurbished
with cartridges just over $20 for 100GB native (240GB 2.4:1).  Even
LTO-1 is very, very difficult to best in performance, only newer Super
DLT320/640 drives can do it -- but are still outclassed by newer LTO-3,
let alone LTO-3, in DTR.

I really consider the LTO-1 to be the "entry point."  If you're not
ready to spend $1K on drive + initial media, then you really shouldn't
be considering tape.  You really don't want to "buy a cheap drive" --
either spend the money for at least LTO-1 or consider non-tape.

E.g., you'd be better off getting some 60-80GB notebook hard drives
(which take G forces 10x better than desktop drives) for ~$100/each and
putting them in small, external enclosures and using external SATA -- or
if that's not an option, USB/FireWire (which is slower/less reliable).

If you have more than 200GB to back up, really just go LTO-3.  LTO-3
really isn't much more than LTO-2, with drives starting around $4,000
now.  If you have a few backup servers to backup over the network, don't
buy a couple of LTO-1 drives -- just get one LTO-3 drive and a dedicated
backup server.  Then diff to that system (which will also give you some
near-line capability).

The sheer DTR of LTO-3 is unbelievable -- 80MBps native -- and really
maxes what Ultra160 SCSI can do.  You can backup a TB in under 2 hours!
LTO-4 will require Ultra320 SCSI, period, and will do a TB in under
ahour!
 
This means that with LTO, when doing network backups, you do _not_ want
to be feeding them "real-time."  *NEVER* do that.  You want to be at
least buffering and, better yet, maintaining a copy of systems on a
dedicated "backup server" with the drive.  Otherwise you will starve the
drive of data.

> I would like something with a net capacity in the 200 GB range
> (i.e. 80 GB native, 208 GB compressed is OK).

LTO-1 is definitely a great entry-point for a single server.  You get
100GB, 20MBps native DTR.  Actual capacity will be around 200-240GB,
with an effective DTR of 40-48MBps.

> NewEgg has media for most of these & their prices are acceptable. 
> Would anyone have any 1st hand reasons to eliminate either 1 of these ?
> TIA

If you have existing AIT or DLT drives, then you might want them.
But if you don't have existing tape assets, just go LTO.

Better, cheaper, faster and because of its commodity proliferation,
you'll be able to get a LTO-4 drive some 10-15 years from now to read
all your LTO-1 and latter tapes.


-- 
Bryan J. Smith           Professional, technical annoyance
mailto:b.j.smith at ieee.org     http://thebs413.blogspot.com
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