On Mon, Apr 27, 2015 at 09:24:47AM +1000, Noah O'Donoghue wrote: > Don't forget the other benefit of hardware raid is being able to boot > from a degraded array.
it's an advantage of software raid too. i've been doing that from software raid for years. in fact, it's one of the reasons i usually have a RAID-1 /boot partition no matter how the rest of the drive space is being used (RAID, ZFS, btrfs, whatever) that flexibility is one of the benefits of software raid - i can decide on a per-partition basis (rather than per-disk) what kind, if any, of RAID i'm going to have. e.g. my current main system has a matched pair of 256GB SSDs - using RAID-1 for / and /boot, and no raid for the swap, ZIL, and L2ARC partitions (RAID makes no sense for those). the bulk data storage is on two 4x1GB ZFS RAID-Z1 pools (mounted as /export and /backup - the latter takes rsync and 'zfs send' backups from all systems on my home network). this wouldn't be possible on hardware raid. (i haven't upgraded the RAID-Z pools to larger/newer drives because the current capacity is adequate for my needs and i'm holding out for SSDs to get *much* cheaper. with luck, the current drives will last until 1 or 2 TB SSDs are affordable to buy in quantities of 4+, or for 4+TB SSDs to be affordable in pairs) > EG if you use software raid and your grub is on a failed drive, you > will have to manually force the BIOS to boot from the other (working) > drive or it will just hang on boot. this might be a problem on ancient hardware, but it's not a problem on anything reasonably modern (for at least the last 5+ years) > For this reason it's worth considering having at least your grub > loader on a RAID partition that uses the hardware RAID controller, > even if the rest of your drives use software RAID. Or being aware of > this limitation, and being prepared to manually boot or boot grub from > an external device if your raid is degraded. or just grub-install to all drives and configure the bios to attempt to boot from each drive in turn. i haven't seen a BIOS (incl. UEFI) for years that doesn't allow you to specify a boot order. craig -- craig sanders <[email protected]> _______________________________________________ luv-main mailing list [email protected] http://lists.luv.asn.au/listinfo/luv-main
