[Discuss] Backing up LVM partitions using snapshots

[richard.pieri at gmail.com (Richard Pieri)]

On 12/16/2011 3:10 PM, Derek Martin wrote:
> Everything has a cost.

Yes, it does.  I'm not saying that tape is free.  I am saying that the 
up front costs of tapes are less than the up front costs for disks, or 
at least they're not not much more.  I am saying that the on-going costs 
for tapes are less than the on-going costs for disks.  And I am saying 
that the expansion costs for tapes are less than the expansion costs for 
disks.

Tapes do require storage space but they don't require constant power. 
They need to be shipped to climate-controlled storage for archival 
purposes but that's a fraction of the cost of running a server 24x7 even 
at Iron Mountain's premium prices.  Tapes are removable so they only 
need one drive, loader or library -- a single major hardware purchase -- 
to handle infinite expansion.


> If you say so, but I seriously doubt that.  But I don't think Mark is
> talking about backing up anywhere near 300TB, so let's make this a bit
> more realistic:  You have one terabyte to back up.  For tape, you
> need:

At my last gig I had a 25TB database with a growth rate of .5TB every 
2-3 months.  Full dumps weekly and incremental dumps nightly with 
indefinite retention as required by SEC regulations.  The backups for 
that database alone would fill up 300TB in just a few months.

At my current gig I have a researcher looking at an initial deployment 
of 50-75TB for staging LHC data for analysis here in Cambridge.  The LHC 
can pump out 15PB a year.

Recall that RAID cage I've brought up several times recently.  That's 
two by 7.5TB RAID6 sets and one by 9TB RAID5 set (I added an external 
storage box recently) and they're using it regularly.  The deltas aren't 
huge in comparison to the total storage but that's still almost 20TB of 
live data in TSM right now.

On a more individual level, I have some 30 Macs and 10 Windows computers 
with home directories backed up nightly.  I'm in the process of 
migrating them from Retrospect to Amanda.  Full dumps for everything 
would fill 1TB of disk and then demand more.  The Linux workstations are 
handled separately via AFS.

Your two-disk solution is appropriate for a personal workstation or a 
laptop or three.  In fact, I use a variant of it at home.  It may be 
barely adequate for a workgroup, and I think that I've demonstrated that 
it's a non-starter for the enterprise.

That's realistic.

-- 
Rich P.