Prox4 and drbd, Raid card and 2 SSD, which way is best for volume creation? TRIM?

[mmenaz]

Hi, as far as I understand drbd9 is over lvm, and I have 2 SSD disks on each server, that I need to "sum" to have their total capacity. I will have an Adaptec 6805e raid controller.
The question is: is better create a raid0 with sdb+sdc at controller level, or create two separate raid0 disks (the controller does not let "single disks") and them use something like vgcreate drbdpool /dev/vdb1 /dev/vdc1 ?
What about trim support? I'm a lot confused about this issue, since I can enable Trim on the guest (fstab), as config flag when creating the VM, and also there is the "scsi-virtio" type of controller stuff that should "pass trims". Finally, drbd is over lvm that I don't know if is of with trims, and if the raid controller passes trim back to storage.
Final question, with DC class ssd (the new Samsung SM863 MZ-7KM960E, hoping to be able to set a better overprovisioning than default), is raid writeback controller cache (with bbu) necessary or not?
Thanks for the advices

 

[wolfgang]

Hi,

I would make a controller level raid it is easier to handle and the performance should be better because the cache.
Trim in in new ssd not really necessary, the controller is handle this.

see following link
https://wiki.archlinux.org/index.php/Solid_State_Drives

 

[mmenaz]

I think the cache will work in any case, with 2 raid0 volumes (that LVM will combine in one) or with 1 raid0 volume (that LVM will see as a single volume).
Or am I missing something?