CDP Backup

DotNetWebs · Jan 20, 2010

My Host is offering a server backup option using this:

http://www.r1soft.com/

I have no experience of CDP Backup so have a couple of questions.

Is it reliable?

What sort of compression does it use? e.g If I have 200GB of space on my server how much backup storage would I require?

Regards

Dotty

FireFleur · Jan 20, 2010

The compressions don't really change too much, on the whole they about tokens using something small to represent a lot.

So, if you have a lot of text then the compression is quite good, lots of patterns, images tend to already be compressed unless it is a bitmap.

The two major compression systems used in Unix tend to be gzip or bzip2, gzip is a little faster and bzip2 tends to squeeze a bit more compression in.

The compression ratio on text hovers around about the 50% mark, and can go to about as low as 35% and as high as say 60% with normal text, depending on the compression algorithm used and the target text.

So, taking the low point 35%, 1GB of text would need 0.65GB of disk space once compressed.

There are more compression algorithms than gzip, and bzip2 but generally the balance is between speed and compression amount. Compression and decompression are also two different procedues so other algortihms may concentrate more on one of those speeds than the other.

You can also gain some advantages in packaging up multiple files into say a tar ball, and then compressing the tar ball generally that would give a better overall results, but is more applicable to the total than one item.

FireFleur · Jan 20, 2010

I just had another look at the page you gave, Block Level restore seems to indicate that CDP may not even use compression, in which case you would need something at least the same size.

They could be using a logical volume, and compression but it looks like it is more like a mirrored system for fast data recovery.

awebapart.com · Jan 20, 2010

My host (unitedhosting.co.uk) uses R1Soft CDP for my company's managed dedicated server (centos), and so far we haven't had any issues, but we have our own backups in place too, using a different backup system, just in case.

I was originally a bit worried that it might slow down the system, especially with database locks, but it seems OK, and does do special things with MySQL database backups. I do not know whether it does similar things with MS SQLServer (if that is what you are using Dotty).

As for space, I thought the point and strength of CDP was to make the backup off-server, so I don't understand why your host would be backing up to the same server.

I also don't quite understand why some hosts who offer CDP also offer single table restores, as that can go against database integrity, but that is a different data integrity issue.

DotNetWebs · Jan 20, 2010

awebapart.com said:
...As for space, I thought the point and strength of CDP was to make the backup off-server, so I don't understand why your host would be backing up to the same server...

Sorry I didn't make that very clear.

Yes it is remote storage but they charge by the storage space. If for example my server has 200GB of disc space used would I require 200GB of storage (or would compression reduce that)?

Regards

Dotty

DotNetWebs · Jan 20, 2010

awebapart.com said:
...but we have our own backups in place too, using a different backup system, just in case...

Same here but I currently only backup my files and data. If i have to restore the server I first have to install and configure a few apps before restoring the data.

What I find interesting about the CDP option is the claimed "Bare-Metal Restore" which would reduce down time and also [probably] provide a more recent restore point.

Regards

Dotty

awebapart.com · Jan 20, 2010

DotNetWebs said:
Yes it is remote storage but they charge by the storage space. If for example my server has 200GB of disc space used would I require 200GB of storage (or would compression reduce that)?

There is mention on the R1soft site about zlib compression, but the level of compression, from no compression to high compression, might be set by the host company (depending on performance and bandwidth factors). Furthermore with any compression, some files wont compress well anyway (e.g. already compressed jpgs, video files, etc).

Your overall requirement also depends on how much of your 200GB disk space is used, and how many separate backups are maintained.

With my server and hosting company I'm getting 4 daily backups kept for 2 weeks, a total of 56 backups, and since it is included in the price I'm glad I don't have to worry about estimating additional backup space requirements or paying extra for it.

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