On 20/01/2010 17:21, Robert Milkowski wrote:
On 20/01/2010 16:22, Julian Regel wrote:
>It is actually not that easy.
>
>Compare a cost of 2x x4540 with 1TB disks to equivalent solution on LTO.
>
>Each x4540 could be configured as: 4x 11 disks in raidz-2 + 2x hot
spare
>+ 2x OS disks.
>The four raidz2 group form a single pool. This would provide well over
>30TB of logical storage per each box.
>
>Now you rsync all the data from your clients to a dedicated filesystem
>per client, then create a snapshot.
>All snapshots are replicated to a 2nd x4540 so even if you would loose
>entire box/data for some reason you would still have a spare copy.
>
>Now compare it to a cost of a library, lto drives, tapes, software +
>licenses, support costs, ...
>
>See more details at
>http://milek.blogspot.com/2009/12/my-presentation-at-losug.html
I've just read your presentation Robert. Interesting stuff.
I've also just done a pen and paper exercise to see how much 30TB of
tape would cost as a comparison to your disk based solution.
Using list prices from Sun's website (and who pays list..?), an SL48
with 2 x LTO3 drives would cost £14000. I couldn't see a price on an
LTO4 equipped SL48 despite the Sun website saying it's a supported
option. Each LTO3 has a native capacity of 300GB and the SL48 can
hold up to 48 tapes in the library (14.4TB native per library). To
match the 30TB in your solution, we'd need two libraries totalling
£28000.
You would also need 100 LTO3 tapes to provide 30TB of native storage.
I recently bought a pack of 20 tapes for £340, so five packs would be
£1700.
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.
Which isn't to say tape would be a "better" solution since it's going
to be slower to restore etc. But it does show that tape can work out
cheaper, especially since the cost of a high speed WAN link isn't
required.
JR
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).
What I really mean is that a disk based solution used to be much more
expensive than tapes but currently they are comparable in costs while
often the disk based is more flexible.
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