Simon,
Pay attention that /boot can be installed only on a single disk or RAID-1 where every disk can actually work as a stand alone disk.
I personally decided to use RAID-5 on 3 disks with RAID-1 on 3xsmall partitions for /boot and RAID-5 on the rest. RAID-5 also allows easier expansion in the future.
On Tue, Nov 10, 2009 at 8:48 PM, Simon Baxter linuxtv@nzbaxters.com wrote:
Thanks - very useful!
So what I'll probably do is as follows...
- My system has 4x SATA ports on the motherboard, to which I'll connect my
4x 1.5TB drives.
- Currently 1 drive is in use with ~30G for / /boot and swap and ~1.4TB for
/media
- I'll create /dev/md2, using mdadm, in RAID1 across 2 ~1.4TB partitions on
2 drives
- move all active recordings (~400G) to /dev/md2
- split /dev/md2 and create a raid 1+0 (/dev/md1) using 4x partitions of
~1.4TB across 4 drives
At this point I have preserved all my data, and created a raid1+0 for recordings and media.
I should now use the remaining ~100G on each drive for raid protection for (root) / and /boot. I've read lots on the web on this, but what's your recommendation? RAID1 mirror across 2 of the disks for / (/dev/md0) and install grub (/boot) on both so either will boot?
On Tue, Nov 10, 2009 at 09:46:52PM +1300, Simon Baxter wrote:
What about a simple raid 1 mirror set?
Ok.. short comparison, using a single disk as baseline.
using 2 disks raid0: (striping) ++ double read throughput, ++ double write throughput, -- half the reliability (read: only use with good backup!)
raid1: (mirroring) ++ double read throughput. o same write throughput ++ double the reliability
using 3 disks:
raid0: striping +++ tripple read performance +++ tripple write performance --- third of reliability
raid1: mirroring +++ tripple read performance o same write throughput +++ tripple reliability
raid5: (distributed parity) +++ tripple read performance
- lower write performance (not due to the second write but due to the necessary reads)
- sustains failure of any one drive in the set
using 4 disks:
raid1+0: ++++ four times the read performance ++ double write performance ++ double reliability
please note: these are approximations and depending on your hardware they may be off by quite a bit.
cheers -henrik
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