We need to install the OS on the 3TB harddisks that come with our Dell servers. (After many attempts, I've discovered that Dell servers won't allow attaching an external harddisk via the PCIe slot. (I've tried everything). )
But, must I therefore sacrifice two hard disks (RAID-1) for the OS? I don't see why I can't just create a small partition (~30GB) on all 6 of my hard disks, do a software-based RAID 1 on it, and be done. I know that software based RAID-5 seems computationally expensive, but shouldn't RAID 1 be fast and computationally inexpensive for a computer built over the last 4 years? I wouldn't think that a CEPH systems (with lots of VMs but little data changes) would even do much writing to the OS partition....but I'm not sure. (And in the past, I have noticed that RAID5 systems did suck up a lot of CPU and caused lots of waits, unlike what the blogs implied. But I'm thinking that a RAID 1 takes little CPU and the OS does little writing to disk; it's mostly reads, which should hit the RAM.) Does anyone see any holes in the above idea? Any gut instincts? (I would try it, but it's hard to tell how well the system would really behave under "real" load conditions without some degree of experience and/or strong theoretical knowledge.)
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