RAID of RAIDS - mirrored RAID 5 -
We bought a Promise SX8000 and configured it as RAID-5 with a hot swap spare to prevent data loss... Then 3 drives failed and we lost the data ;-) So we sent out emails saying the database was down because:
"we purchased a very large expensive highly redundant storage device which failed.. so we yelled at promise who is sendind us a second very large expensive highly redundant storage device so that we can make one out of the two in hopes it works"
Ok, I have heard reference to things like RAID-52 at such, (redundant raid 5's) but my queston is this..
If we have 2 Promise SX8000 external RAID's configured in a RAID-5, each about 1TB and we wanted to mirror one to the other, where do we start? We thought we could just buy a card, and hook up both of the Promises to it, so we did... The card sees the devices, but wont make a mirror out of them. We called Promise who said no, it couldnt be done - thay had tried a RAID-5 of RAID-5's which failed miserably - so we called Adaptec (the card we bought) who said it was promises fault, their devices werent presenting themselves as SCSI devices and of course Promise says they are.
Has anyone ever set up somethign similar to this, or have an Idea where to send me? Currently we are going to have to write some cron josb to backup one to the other at midnight, meaning if we fail we only lose the current days work - but it seems like there is a better way to do this..
Here's a possible lead for you.
I am no expert in either Linux or *BSD, but I have read about something FreeBSD offers called "vinum" which, as I understood the description, sounds like it might be able to do something like what you want. I don't think I have ever seen anything of the sort for Linux. It might be a lead to something useful.