Replication vs. Backup

[Steerpike58]

I bought two identical Buffalo LS410D models with a view to locating them in two separate locations, and having them mutually back each other up; that is, replicate to one another. To further clarify, additions / changes / deletions to one would reflect on the other, and vice versa. No one device is 'primary' or 'master'.

I can see that you can back up one link station to another over VPN. This is a feature of the 'backup' solution built in. But that is inherently 'master/slave' or 'push' in nature; one device is the 'master', and all changes are 'replicated' to the backup or 'slave' device. But you can't also have changes made on the 'slave' or 'backup' device replicate to the 'master' device - is that true?

Is there a 'replicate' feature anywhere in the system?

Also - does the device support 'plugins' or add-on apps?  I was hoping to add an rsync-like tool.

Also, I found this page on buffalo's site: http://en.faq.buffalo-global.com/app/answers/detail/a_id/14727/p/31,33 - how to set up Web Server on LinkStation.  While I don't want to setup a webserver, I was intrigued by the implication that the LS could do such things. The instructions include "Navigate to Network / Web Server ..." and "Navigate to Network / MySQL server ...' - but my box doesn't have these options.  Were these features removed? Do I need to purchase a more expensive version of the LS to get these features? Or, as I was hoping, is there a 'plugin' concept that allows me to add additional options to the base feature set?   I'm more than happy to send the two units back and buy a more expensive model, if that's what is needed.

Thanks!

[Steerpike58]

Updating my original post after additional research:  I see that the Terrastation 3000 line seems to offer Replication. Looks like Terrastation 1000 line does not. So Terrastation 3000 seems to be 'minimum cost of entry' to get replication going - is that true?

I'm still curious about my other question above, relating to plugins (webserver, MySQL server, etc).

Thanks!

[Texturtle]

The article you saw on LinkStation is likely for an older model, current LinkStation models do not have this functionality.

All TeraStation support replication. It's considered a part of the TeraStation system.

[davo]

I'm still curious about my other question above, relating to plugins (webserver, MySQL server, etc).

You can't add on services on these units, what they come with is what you are stuck with. Older Linkstations had webserver, MySQL server, etc but not anymore, these are only available on the Terastation range now.

[Steerpike58]

The article you saw on LinkStation is likely for an older model, current LinkStation models do not have this functionality.

All TeraStation support replication. It's considered a part of the TeraStation system.

If you visit this Buffalo page: http://www.buffalotech.com/products/category/network-attached-storage-nas/nas-for-business-terastation ,
and then click on 'compare' below, say, the 3000 and the 1000 model lines, you get a table that includes this:

                                       1000    3000
iSCSI Support                    No       Yes
Peer to Peer Replication      No       Yes
Cloud Backup Support        No       Yes

So is that comparison table wrong?
Also, I note the 1000 series has a CPU "1.2 GHz Dual-Issue ARM" while the 3000 has a CPU "1.33 GHz Dual-Core ARM". What does 'dual issue' mean (I know what 'dual core' means)?

Thanks!

[davo]

Dual issue means that each clock cycle the processor can move two instructions from one stage of the pipeline to another. Where this happens depends on the processor and the company's terminology: it can mean that two instructions are moved from a decode queue to a reordering queue (Intel calls this issue) or it could mean moving instructions (or micro-operations or something) from a reordering queue to an execution port (afaik IBM calls this issue, while Intel calls it dispatch)

But really broadly speaking it should usually mean you can sustain executing two instructions per cycle.

[Texturtle]

And yes, the comparison chart is wrong. I'll let the administrator know that needs to be corrected.

[Steerpike58]

...
All TeraStation support replication. It's considered a part of the TeraStation system.

In reading the manuals online, it appears that the 'replication' supported is between two Terastations physically connected by an Ethernet cable (2nd LAN port on primary NAS). Is this true? I want to setup replication between two NAS devices in physically different locations (connected via VPN). Is that possible with any of the Buffalo models? Or do I have to use 3rd party software running on a workstation / server for that?

[Texturtle]

Here are the KB articles on replication setup. Using a direct connect cable is only recommended in the event that you plan to set up failover.

http://www.buffalotech.com/knowledge-base/terastation-replication-setup

[Steerpike58]

Here are the KB articles on replication setup. Using a direct connect cable is only recommended in the event that you plan to set up failover.

http://www.buffalotech.com/knowledge-base/terastation-replication-setup

Excellent, thanks.  I presume I can 'seed' the replication locally, then reconfigure the job later after relocating the target NAS to a remote location. What criteria are used to determine a file change? Is there some kind of checksum maintained, or is it simply date/timestamp? My NAS devices will be located in two timezones.

[Texturtle]

The system uses rsync to transfer files and determine which files need to be copied. Yes, you should be able to run the first replication locally and then relocate one unit.