On 20/01/2010 10:48, Ragnar Sundblad wrote:
On 19 jan 2010, at 20.11, Ian Collins wrote:
Julian Regel wrote:
Based on what I've seen in other comments, you might be right. Unfortunately, I
don't feel comfortable backing up ZFS filesystems because the tools aren't
there to do it (built into the operating system or using Zmanda/Amanda).
Commercial backup solutions are available for ZFS.
I know tape backup isn't sexy, but it's a reality for many of us and it's not
going away anytime soon.
True, but I wonder how viable its future is. One of my clients requires 17
LT04 types for a full backup, which cost more and takes up more space than the
equivalent in removable hard drives.
In the past few years growth in hard drive capacities has outstripped tapes to
the extent that removable hard drives and ZFS snapshots have become a more cost
effective and convenient backup media.
LTO media is still cheaper than equivalent sized disks, maybe a factor 5 or so.
LTO drivers cost a little, but so do disk shelves. So, now that there is no big
price issue, there is choice instead. Use it!
Hard drives are good for random access - both restore of individual files and
partial rewrite.
Hard drivers aren't faster than tape for data transfer, but they might be
cheaper to run in parallel and therefore you could potentially gain speed. Hard
drives have shorter seek time, which may be important.
Hard drives are probably bad for storing for longer times - especially - you
will never know how long it could be stored before it will fail. A month?
Probably. A year? Maybe. Five years? Well... Ten years? Probably not. LTO tapes
are supposed to be able to keep it's data for at least 30 years of stored
properly. Hard drives are probably best when used online or at least very often.
So - it is wrong to say that one is better or cheaper than the other. They have
different properties, and could be used to solve different problems.
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
--
Robert Milkowski
http://milek.blogspot.com
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