[Beowulf] Re: OT: LTO Ultrium (3) throughput?

Gerry Creager gerry.creager at tamu.edu
Mon Jul 7 07:29:48 EDT 2008


Jon Aquilina wrote:
> in my case where money isnt an issue wouldnt it be better for me to 
> build a raid backup array? i understand your reasoning. im still 
> studying and fairly new in the higher education of IT so when i start 
> working ill keep what you mentioned to heart. only problem is that where 
> i am located in europe things are more expensive here. another random 
> idea why not create a raided backup array backed up to tape? is it 
> possible to do a tape back up of data thata being written to disk instantly

It's absolutely possible to do a mirrored write to RAID spinning media 
and also to tape.  In a perfect world, where I don't have budget 
constraints, that's how I'd achieve my third tier of backup.    The real 
reason we bother with tiered storage and multiple copies, however, 
remains "disaster recovery".  One theory says that simply having two 
copies in the data center is enough.  Experience teaches that, for true 
disaster recovery, one needs a pretty recent off-site copy, that is 
unlikely to be disrupted by an event in one locale.  I know of one 
company that mirrors disks over 100 miles from their r&d/corporate 
offices via multiple 10gigabit paths, with two feeds for power, a diesel 
generator, and a battery plant to keep things running.  In their main 
site, they have disk and tape.  Offsite, they have another disk copy. 
And last week's tapes.

In higher-education IT, one tends to have a lot of budget constraints. 
Funding agencies want accountability and don't seem to just give us 
hardware dollars for the asking, although it often seems that way when 
someone who's not seeking said funding, watches the process.  Therefore, 
money IS a problem and we have to determine the best way to keep things 
going while optimizing expenses.

Different approaches don't mean we're disagreeing with you, however.  MY 
primary backup is spinning (RAID) disk.  I'd like to expand to LTO tape 
with robotics but my funding agencies have not yet seen the wisdom of 
this, and think my use of disk is just fine.  Until we have a problem 
(and problems are almost guaranteed) and get in trouble for not having 
incorporated tape (or another, different, technology) in our backup 
plan, I don't expect to see funds for it. In fact, when we do get in 
trouble, I see us redirecting already allocated funds rather than 
getting new funds, to accomplish this.  Just understand that redirecting 
  funding for a new hardware implementation requires sponsor approval, 
and if they don't understand "Why?" it can get messy.

gerry

> On Mon, Jul 7, 2008 at 5:05 AM, Steve Cousins <cousins at umit.maine.edu 
> <mailto:cousins at umit.maine.edu>> wrote:
> 
> 
>         From: "Jon Aquilina"
>         this is slightly off topic but im just wondering why spend
>         thousands of
>         dollars when u can just setup another server and backup
>         everything to a
>         raided hard drive array?
> 
> 
>     Another RAID system helps but only if it is located somewhere else.
>     The main reason we backup is for disaster recovery. One nice thing
>     about tape is that you can take the tapes to another location easily
>     or put them in a fire safe.
> 
>     Another reason is that RAID systems don't scale up as easily as a
>     tape system. Our library has two 15 tape magazines that can be
>     removed and replaced. It costs about $750 to buy 15 new tapes plus a
>     magazine. That's not too bad for 6 TB of storage (uncompressed, with
>     HW compression we get about 9 TB). Plus it takes practically no time
>     to start using it.
> 
>     The library wasn't really that expensive when we bought it either.
>     Somewhere around $7500. At the time we bought that we were using 400
>     GB drives in our RAID systems at $300 each. To build a server with 5
>     TiB (usable) of RAID storage at the time was about $7000. The tapes
>     were more expensive then (about $100 each) but for about $10,500 we
>     got 12 TB of tape storage (library plus 30 tapes). To get roughly
>     the same of disk storage would have been about $14K. So right off
>     the bat tape was cheaper. Plus it is so much easier to manage. I
>     like the idea of snapshots and using rsync plus links is a crafty
>     idea but I sleep better knowing that I have a "real" (one that I can
>     carry around) backup of our data in our safe.
> 
>     Steve
> 
> 
> 
> 
> -- 
> Jonathan Aquilina
> 
> 
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> 
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
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