Rodrigo Barbosa rodrigob@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."