[CentOS] Harware vs Kernel RAID (was Re: External SATA enclosures: SiI3124 and CentOS 5?)

Les Mikesell lesmikesell at gmail.com
Wed Jun 3 12:52:07 UTC 2009

Michael A. Peters wrote:
> I guess from the discussion that hardware raid is definitely still the 
> way to go for servers, where the guy at the colo can simply swap out a 
> dead drive if need be w/o any serious downtime etc.

On the flip side, you generally have to install some vendor-specific 
tool to monitor the status of the drives in a hardware raid if you 
aren't in a position to look at the lights on the front where a simple 
'cat /proc/mdstat' will show software raid status. And it's not all
that hard to ssh in an run an mdadm command after the 'hands on' colo 
guy swaps the drive in for you.  You do need swappable drive carriers, 
and SCSI controllers usually need another command to re-probe a device.

> What I'm personally interested in doing is building an amanda server for 
> my home network, backing up /home and /etc from my 3 other computers, 
> but virtual tapes (disk images) instead of real tapes, once blueray 
> media becomes cheap enough to burn the virtual tapes as a secondary 
> backup, but I primarily want the virtual tapes stored on a redundant 
> raid so that recovering will be easier (no need to go from blue ray 
> unless the raid failed)

I'd recommend looking at backuppc instead of amanda if you mostly want 
on-line storage.  Its storage scheme will hold a much longer history in 
the same amount of space and it has a handy web interface for browsing 
and restores.  It can generate a tar-type archive output for tape/dvd, 
etc., but it is really designed around the on-line storage.  And yes, 
you do want it on some kind of raid.  You might even want to plan to 
periodically break the raid and swap a member drive offsite since the 
storage format packs so many files with hard links that it is difficult 
to copy the whole thing in other ways.

   Les Mikesell
     lesmikesell at gmail.com

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