[CentOS] Re: Planning Mail Server (with low resources)

[Bryan J. Smith]

Rodrigo Barbosa <rodrigob at suespammers.org> wrote:
> At least around here, a 120G DLT tape costs less than half
> the price of an HD of the same capacity.

Reality ...

When you're talking 100GB, most of the higher capacity,
leading-edge technologies are $50-100/cartridge, _regardless_
of the capacity.  So you're better off going with the
latest/fastest/biggest capacity when you're going to spend 4
figures.

Right now, that's multi-vendor LTO revision 3 -- 400GB
(800GB) at 80MBps (160MBps) native (2:1 hardware).  DLT is
slower and largely uni-vendor, HP, and even HP does LTO (and
they do it better than DLT).  DLT should only be considered
for legacy media compatibility.

More commodity 8mm AIT-2 and VXA-2 drives are just under
$1,000, and are under 100GB, but then the tapes are still
costly.  So you have to consider where your "break even"
point is when it comes to cost.  For a single server, or a
single backup server, that will only putting less than 100GB
(so only 1 tape) maybe 1-2 times/month, you're okay.

But if you need to off-site more than 100GB from multiple
servers, make the $7-8K investment in TBs of disk storage on
a dedicated backup server with a dedicated LTO-3 drive. 
Especially if you're putting 1+TB off-site, so it's 6+
tapes/month, possible dozens.  The cost per GB per cartridge
is well worth the LTO-3 initial cost.

> Not to mention that tapes are much more reliable, since you
> can store them on appropriate containers/safes.

Yes, the whole reason for Removable Rigid Disk (RRD).  3.5"
fixed disk cannot only not take the Gs, but it is _not_
designed to be off-line for weeks or months -- especially not
after being rattled around.

Now 2.5" fixed disks are getting better G tolerances, and are
an interesting option.  80GB 2.5" disks go for under $100, so
they are an option for smaller companies.  I might recommend
them in limited cases over going with extra on-line/near-line
disk and a VXA-2 or AIT-2 drive.

> They also don't have mechanical parts built in, so the they
> are less likely to fail.

Well, there _are_ still moving parts, just no mechanics. 
Some of the new 1" hard drives are less fragile, taking even
800Gs.

> Of course, I mean good tapes, not the el-cheapo ones.

By "el-cheapo" you mean?

4mm (DAT), QIC (?), 8mm (AIT, VXA), HIC (LTO?), [F]IC (DLT)
-- there's a number that share the same moving part design.

> HDs are not a reliable backup media, and never were.

Commodity 3.5" fixed disk is designed for regular operation
and limited G-forces, even with heads parked.

> This is enough to show me it would be a waste of time to
> show the flaws on your thinking. If you are looking at it
> emotionaly, it is useless to explain anything to you.

Disk and tape are not a versus, they are a complement.

That's why I wrote the 2005 September Sys Admin article on
VTLs, they are the evolution of _complete_ backup.

I guess I need to follow up with a blog entry on "scenarios."



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Bryan J. Smith                | Sent from Yahoo Mail
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