Clarification needed for SSD and DRBD setup (2 node, prox 4.0)

[mmenaz]

Hi, we are going to setup 2 node cluster like this:
Both nodes with EACH
- Adaptec 6805E Raid controller set as JBOD (and put in writethrough since will not add BBU)
- 1 Intel dc 3710 200 GB for Proxmox installation
- 2 x Samsung DC 845 PRO 800 GB for storage
- 1 Intel 10 GB nick adapter

We will use Proxmox 4.0 (currently Beta, probably stable at the time of the real deploy).
We will save (a lot of) money in high end RAID controller cache and BBU since SSD has "power loss protection" and should be "fast enough"
Is the first time I will use DRRBD, and I choice 2 SSD to prevent difficult "split brain" scenario (each node will run some vm in a specific ssd only, i.e. node 1 will only run Vms on ssd1, and node2 on ssd2)
Some things that I don't understand are:
- do SSD have to be manually "overprovisioned" for better durability? (if so, with Samsung "magician" tools or is there generic and GNU ways to do so? I.e. partition not to the full capacity is ok?)
- how trim works with DRBD over LVM? Do I have to set trim inside the KVM guests and that's all?
Finally, any obvious mistake / better alternative (but please reply to above questions as well)?
Thanks a lot

 

[adamb]

Ive never been a fan of "over-provisioning". I would just prefer to purchase a drive which can handle the write workload you are looking to utilize. Typically you just leave free space on the drive.

I know DRBD supports trim now, but I am unsure how to utilize it. On the host side im pretty sure you will need to install the OS as ext4 for trim support.

I am also assuming you arn't looking for HA functionality as you are only going with two nodes.