tape capacities

hi

could someone help me out here?

i need to work out how many LTO3 tapes it will take to hold 12TB data.
can someone please tell me if the following calculation is correct or
show me a batter way of working this out?

LTO3 holds 400GB

12 x 1024 = 12288GB
12288GB / 400 = 30.72 tapes = 31 tapes required

----

also, could someone please let me know how i can calculate how fast i
can write the 12TB data using LTO3s please

thanks

sorry, what i mean by the second question is what's the formula to work
out how long it will take to transfter x amount of data to a tape drive
that will do 136MB/sec

deggs wrote:
hi

could someone help me out here?

i need to work out how many LTO3 tapes it will take to hold 12TB data.
can someone please tell me if the following calculation is correct or
show me a batter way of working this out?

LTO3 holds 400GB

12 x 1024 = 12288GB
12288GB / 400 = 30.72 tapes = 31 tapes required

----

also, could someone please let me know how i can calculate how fast i
can write the 12TB data using LTO3s please

thanks

On 9 Aug 2006 12:05:04 -0700, "deggs" wrote:

sorry, what i mean by the second question is what's the formula to work
out how long it will take to transfter x amount of data to a tape drive
that will do 136MB/sec

deggs wrote:
hi

could someone help me out here?

i need to work out how many LTO3 tapes it will take to hold 12TB data.
can someone please tell me if the following calculation is correct or
show me a batter way of working this out?

LTO3 holds 400GB

12 x 1024 = 12288GB
12288GB / 400 = 30.72 tapes = 31 tapes required

----

also, could someone please let me know how i can calculate how fast i
can write the 12TB data using LTO3s please

thanks

Is it 400GB native? If you're counting compression you may be short,
depending on your data. If that's a native number then it's simple
math, just like you did.

Also, it's the same simple math for transfer rate.

if it's 136MB/sec. You've 12,582,912MB to transfer. 12,582,912/136 =
92,521 seconds. So basically 25 hours.

~F

deggs wrote:
hi

could someone help me out here?

i need to work out how many LTO3 tapes it will take to hold 12TB data.
can someone please tell me if the following calculation is correct or
show me a batter way of working this out?

LTO3 holds 400GB

12 x 1024 = 12288GB
12288GB / 400 = 30.72 tapes = 31 tapes required

It depends on the data. If you're talking about large fragments of
data and you're not doing any compression, then you may be close to
right. If you're going to small individual fragments with no
compression, you'll need more tape. If your data can compress well,
then you probably need fewer tapes.

also, could someone please let me know how i can calculate how fast i
can write the 12TB data using LTO3s please

That *really* depends and there are a lot of factors involved.

.../Ed

deggs wrote:
sorry, what i mean by the second question is what's the formula to work
out how long it will take to transfter x amount of data to a tape drive
that will do 136MB/sec

I haven't heard of an LTO3 drive that will write at 136MB/sec. You'll
be lucky if you get half of that. And, you need to factor in how fast
you can read the data from disk, how you're going to write it to tape,
and what you're doing about cataloging the data. You may get as low as
10MB/sec to 60MB/sec. You may not even be able to physically read
the data off of your file system at 136MB/sec,.

.../Ed

thanks everyone for your answers

HVB wrote:
On Wed, 09 Aug 2006 20:04:16 GMT, Faeandar wrote:

Also, it's the same simple math for transfer rate.

if it's 136MB/sec. You've 12,582,912MB to transfer. 12,582,912/136 =
92,521 seconds. So basically 25 hours.

That's assuming you can constantly stream data to the tape at that
rate... which is not easy unless it's from a high speed source. I'd
suggest allowing a wide error margin on this unless you know for sure
you're going to hit that streaming target.

HVB