I am sure I have blathered about this before...
Something I looked at at a previous job (they didn't bite) was replacing
a hodpodge of physically dying servers with a pair of modern servers,
each big enough to carry the load, but set up rather redundantly. More
recently I was thinking I might do something related to replace my own
basement server(s).
The rough idea:
- Each box does Linux software raid 1 (on disks from different
manufacturers) to cushion against a dead disk.
- On top of the raid (and probably some LVM) is DRBD in a hot/spare
arrangement, so a single filesystem can be seen from each box. (But not
a clustered filesystem, seems no point, instead just do a shift of which
box gets to talk at any point.
- Each box has a dedicated fast ethernet link to the other for DRBD
syncing.
- Use KVM for virtualization of guest VMs, and live migration between
the two boxes.
- Dual /-partitions on each box so the host OS can get upgrades that
can be quickly be reverted with a reboot.
- If inside the VMs I want to do dual /-partitions, that might be
smart, too.
- Some attention to physical dispersal: like external USB 3 or ESATA
disks, so a single smoking event doesn't necessarily smoke everything.
Put the second box at some physical distance, too.
- UPSs to keep the boxes running through power outages. Maybe
hibernate to disk when the power runs out?
- And some thought about how to snapshot and backup VM data, even haul
offsite if I want to be extra good. Ping-pong between two encrypted
backup disks. I crafted that once, too.
Not a high performance model but a high availability model that doesn't
care much about what happens inside the VMs. A given VM that isn't
otherwise interested in rebooting might be run for years in such a rig.
The Shuttle's DS61 V1.1 looks like a nice way to build a minimal array
like this.
-kb
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