Re: [PLUG] Two-Drive Software Raid 5?

[Rich Freeman <r-plug@thefreemanclan.net>]

On Mon, Jan 3, 2011 at 10:38 PM, Rich Freeman <r-plug@thefreemanclan.net> wrote:
> Is it a given that modern SATA drives still support 1.5Gb/s?  Or, do I
> need to make sure the drive supports this or has a jumper?

Just for list closure:

1.  I did some research and did confirm that very old SATA-I
controllers, like the VIA VT6420 on my motherboard, do NOT support
SATA-II drives, and will NOT auto-negotiate.  The drive must support
SATA-I, either via some kind of atypical fancy firmware or a jumper.

2.  My current plan is to run mdadm RAID-1 + LVM + ext4 on the drives.
 I don't think they use 4k sectors but I'll align everything on
8-sector boundaries just in case.  I can always use the link that was
posted to switch it to RAID-5 later if necessary, and do tests
beforehand/etc.

I did some research on btrfs - it just isn't ready for prime time yet,
except for data which is disposable, or which is readily backed up /
restored.  Hopefully in a year it will be there, but I wouldn't trust
it yet.

I feel like I'm already trying the fates again by going to LVM.  I had
a really bad experience with it a few years back - I had a system
lockup/reset while the underlying RAID was degraded and somehow the
metadata got corrupted.  I did an fsck on one logical volume and ended
up scrambling data on a different logical volume, demonstrating that
LVM had somehow gotten them mixed up.  I did some googling and found
one or two other reported cases of this, but it is extremely rare.
Hopefully today with barrier support and NCQ that is much less likely
to happen.

Thanks to those who replied!  If anybody has any tips feel free to
send them my way - I probably won't be doing anything until the
weekend (crossing my fingers that my old PATA drives hold out until
then - RAID is nice but doesn't help if drives start abusing the bus
on cheap non-hotswap hardware).

Rich
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