building a RAID system
xyzzy at speakeasy.org
Thu Oct 9 05:25:18 EDT 2003
On Thu, 9 Oct 2003, Alvin Oga wrote:
> > > backup is hard. you can get 160 or 200G tapes, but they're almost
> > > as expensive as IDE disks, not to mention the little matter of a
> > 100GB LTO tapes can be had for $36, that's less than half the price of the
> > cheapest 200 GB drives.
> we/i like to build systems that backup 1TB or 2TB per 1U server ...
> - tapes doesn't come close ... different ballpark
How do you stick 2TB in a 1 U server? I've seen 1U cases with four IDE bays,
and the largest IDE drive I've seen is 250 GB.
I've got two 4U rackmount systems sitting side by side on the same shelf. One
is a ADIC Scalar 24, which holds 24 100 GB LTO tapes. The other is a 16 drive
server with 200GB SATA drives and two 8 port 3ware cards. The tape library
has 2.4 TB and the IDE server is 3.2 TB. To be fair, the IDE server is brand
new, while the ADIC is around a year old. If the tape library were bought
today, it would have a LTO-2 drive with double the capacity and could store
4.8 TB. So tapes seem to come pretty close to me. It also quite a bit more
practical changes tapes with the library than to be swapping hard drives
around. The libraries built in barcode reader keeps track of them all for me.
I can type a command and have it spit out all the tapes that a certain set of
backups are on. They fit nicely in a box in their plastic cases and if I drop
one it will be ok. I can stick them on a shelf for five years and still
expect to read them. And the tapes don't take up any rackspace or power or
need any cooling. I've never had a tape go bad on me either, even though I've
been though a lot more of them than IDE drives.
Of course the tape library was expensive. A new LTO-2 model can be had for
around $11,600 on pricewatch. The 16 bay IDE case, CPUs/MB/memory and 3ware
controllers were much less. But the cost of the media is a lot less for tapes
than for SATA hard drives. Especially if you get models with 3 year
warranties. Once you buy enough drives/tapes you'll break even on a $/GB
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