On Jan 20, 2010, at 12:21, Robert Milkowski wrote:
On 20/01/2010 16:22, Julian Regel wrote:
[...]
So you could provision a tape backup for just under £30000 (~
$49000). In comparison, the cost of one X4540 with ~ 36TB usable
storage is UK list price £30900. I've not factored in backup
software since you could use an open source solution such as Amanda
or Bacula.
[...]
You would also need to add at least one server to your library with
fc cards.
Then with most software you would need more tapes due to data
fragmentation and a need to do regular full backups (with zfs+rsync
you only do a full backup once).
So in best case a library will cost about the same as disk based
solution but generally will be less flexible, etc. If you would add
any enterprise software on top of it (Legato, NetBackup, ...) then
the price would change dramaticallly. Additionally with ZFS one
could start using deduplication (in testing already).
Regardless of the economics of tape, nowadays you generally need to go
to disk first because trying to stream at 120 MB/s (LTO-4) really
isn't practical over the network, directly from the client.
So in the end you'll be starting with disk (either DAS or VTL or
whatever), and generally going to tape if you need to keep stuff
that's older than (say) 3-6 months. Tape also doesn't rotate while
it's sitting there, so if it's going to be sitting around for a while
(e.g., seven years) better to use tape than something that sucks up
power.
LTO-5 is expected to be released RSN, with a native capacity of 1.6 TB
and (uncompressed) writes at 180 MB/s. The only way to realistically
feed that is from disk.
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