When it comes to replicating a LUN or partition to a physically separate server, Linux has DRBD (now in the kernel!). As I understand it, it has both synchronous and asynchronous replication modes. When you have a fast network between your two servers, it can rock hard.
I need to do the same thing for Windows servers. I know there are non-free packages that do this (recommendations would be nice), but considering what we call a 'budget' around here, I need to know more about the more free options. If any.
We're on Server 2008 for the large majority of our storage servers. If R2 will get us what we need, I need to know now so I can schedule the upgrades in 4 weeks.
The crux of the problem is that I need to replicate a bunch of LUNs stored on an HP EVA 6100 (10K RPM disks) and EVA 4400 (mostly the, er, 1TB FATA drives) devices to something else. Now HP has the very nice Replication Manager that'll handle replicating between the two, but we're trying to wean ourselves off of the soon-to-be-end-of-lifed 6100. We need to replicate to something that isn't an EVA.
According to my performance monitoring, the largest part of our storage to be replicated is accessed in a very bursty way (it's file-server data). Backup I/O dwarfs regular I/O by a factor of three. The total amount to be replicated is around 7TB, with a daily file net-change on the order of 500GB (all those Outlook PST files add up). I don't know what the block-level net-change is.
We have Fibre Channel available, and in one datacenter we even have the beginnings of an iSCSI isolated network. But between our two datacenters we are (currently) limited to a single 1 GigE pipe, that will be upgraded to a 10 GigE pipe within the next 12 months.
There are some off-the-shelf utilities out there, I just don't know much about them
Double-Take Availability Seems to do something like block-level replication, but not quite. Could be what I'm looking for.
Veritas Storage Foundation Seems like serious overkill for this particular problem, but would add a lot of flexibility to our environment.
CommVault Simpana Heterogeneous replication, WAN friendly.
And many, many more.
If this environment were Linux with Samba, DRBD would be a near perfect fit. I just don't know if there is an equivalent on the Microsoft side of the house.