ADSM-L

Re: How do you back up 2 PB of data?

2002-11-19 12:55:02
Subject: Re: How do you back up 2 PB of data?
From: Dan Foster <dsf AT GBLX DOT NET>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Tue, 19 Nov 2002 17:51:52 +0000
Hot Diggety! Orville Lantto was rumored to have written:
> A 72 drive, 10 I/O slot 3584 library will hold 2207 cartridges.  with 175
> GB/cartridge that works out to 6 libraries.

Aye, in terms of tape capacity. However, if you have a requirement that
it finish an entire full backup in a single day -- say, 20 hours...and
you get between 15-30 MB/sec for HW compressed writes with the LTO drives.

So we pick a common number that's actually sustainable in real life: 22.5
MB/sec.

22.5 MB/sec * 72,000 seconds (20 hrs) * 72 drives * 6 libraries =

683,438 TB, or about 32.6% of 2 PB. Therefore you need 3 times the
original number of 6 libraries, and that's assuming you can keep up
this rate constantly for every single second of 20 hours.

18 fully decked out 3584 libraries would be something to behold, I think ;)
That'd span 106 frames and 1,296 LTO drives. A single full backup would
run about $18M (list price) worth of tapes in that kind of configuration.
I'd like to work for a place that can afford it! Even after deep
discounting, that's still $8-10M worth of tapes.

-Dan

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