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Old 29th October 2009
roundkat roundkat is offline
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Default Hard Drive backup

I am replacing 2 machines
1 - OpenBSD (single drive)
Webserver, SMTP Gateway, Dhcp Server
1 - linux (currently has a hardware RAID) card
Email server for 10 users
with
1 - OpenBSD box, with 2 disks to do the same task.
I know that OpenBSD does not support "Root on Raid" as of yet.
My question
What is the best way to "mirror" the primary disk so that in case of
disk failure I can just move the second disk to the primary and then
use it ?
This would be a manual process , not looking for any automatic fail over

I have considered just loading the OS on each disk then putting the second on
as a slave disk and then just rsyncing the changes over to it..

Thoughts.. ???
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Old 29th October 2009
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jggimi jggimi is offline
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OpenBSD supports root-on-RAID, and has for years, in two ways:
  • Hardware RAID. These appear as standard bus devices to the OS. If these hardware devices can register with the bio(4) driver, they can also be managed via bioctl(8). The bio(4) man page lists all of the currently supported hardware RAID technology that can be managed with bioctl.
  • Software RAID via RAIDframe. One cannot -boot- from a RAID set, but one can certainly configure -root- on RAID.
There probably isn't a "best" way; but the easiest would be a hardware RAID, I would think.

I use RAIDframe with root-on-raid with one of my systems, and have had many disk drive problems, but never an outage due to them.

I set that RAIDframe server up so it notifies me via e-mail when a failure occurs. I've been e-mailed many times. Each time, I have been able to recover with the same hardware (forcing bad blocks to reallocate before returned the failed drive to the RAID set) or if necessary swap drives, and all without data loss. I have to take a scheduled outage to swap drives, though, as they are not hot swappable.

I have also used raidctl(8) to intentionally break the RAID 1 mirror to manage risky software upgrades/reconfigurations, as recovery is faster than doing a complete restore.

(RAID sets are not backups. But you already know this.)

Last edited by jggimi; 29th October 2009 at 06:39 PM.
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Old 29th October 2009
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jggimi jggimi is offline
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Two additional notes:

1 -- I did not mention softraid(4), as it is not quite ready for production, since there is no recovery method for components of a RAID set. The admin must back up, rebuild, and restore, which will usually introduce significant downtime. Though it, like RAIDframe, cannot boot from a RAID set but can easily have root on RAID.

2 -- There are other replication technologies, but those are more commonly used over a network, not from one drive to another. One example is rsync. These remote replication technoligies will introduce data loss, which must be managed, and specific implications for data loss management will be unique to each application environment.
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Old 29th October 2009
roundkat roundkat is offline
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jggimi... Thank you for the reply..

I have read much about raidframe and even tried it back in the
3.3 days.. but never got it to work..
Also, did know about softraid that was yet supported on i36 yet..

I should have clarified that the hardware card in the Linux box is
a 3Ware which Theo hasn't much respect for , 3ware uses the
twe(4) driver and the card I have is supported by that driver.

Funny, I actually sent Theo a message (and he responded) about
LSI providing source code for the 3ware/AMCC cards and would
the OpenBSD devs update the twe(4) driver.

Theo's response was "... If they approach us ..."

Also , I use rsync to mirror all my websites to each other which
does provide backup /redundancy, all boxes are at different locations..

I may go ahead and use the RAID card and then do my backups via
rysnc script since I already have that structure in place..

Thank you for the info regarding bioctl(8)...

Was just curious about what others were using..

rk
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