On 6/29/10, Karanbir Singh mail-lists@karan.org wrote:
Depends on how you set it up, if you have 2 machines ( disk nodes ), exporting iscsi. 1 machine ( data node ) doing the import and sets up a raid1; you can afford to have one of those two machines down. You *cant* afford to have the data-node down. Thats where the filesystem lives. You can potentially have the same disks from the disk-nodes imported to a standby data node using something like drbd over the mdraid setup. Alternatively, you can look at using a clustered filesystem and have it go X way. But then you may as well use something like gnbd with gfs2 instead(!).
Looking up gfs2 was what lead me to glusterFS actually and because glusterFS had all the RAID stuff pointed out upfront, I stopped reading about gfs2. Googling gluster then lead to openFiler which then seemed like a simpler way to achieve the objectives.
Yes, lots of options and different ways of doing the same thing. So start at the top, make a list of all the problems you are trying to solve. then split that into 3 segments:
- Must have
- Good to have
- Dont really need
Must have - low cost, clients have a budget which was why mirroring all the machines is not an option - data redundancy, application servers can go down, but data must not be lost/corrupted. - expandable capacity - works with VM - doable by noob admin :D
Good to have - able to add/restore capacity without need to take down the whole setup - application server redundancy - webUI for remote management
I've done mostly LVM + mdraid setup so far, hence the openfiler + remote iSCSI raid route looks to fit the above and is the most simple (less new things to learn/mess up) option compared to most other which needs multiple components to work together it seems.