[NTLUG:Discuss] Re: looking for raid & controller advice -- "FRAID" card = "software RAID"

[Bryan J. Smith]

On Sun, 2004-12-05 at 17:04, Kevin Brannen wrote:
> If I build the file server, pulling from the file server to burn is 
> probably the only "easy" way to make it work.  I'm just the visionary 
> and sysadmin.  The people who do most of the burning work are not 
> technical, and the burning software is not very sophisticated...sigh.

Then automatically rsync to a local directory, script it to an icon,
etc...  You can automate a lot directly in Samba, via Server Side
Automation.

> Oh, you can logically split a card?  Hmm, you're going to have to stop 
> giving me options; my head is going to explode! ;-)

The 3Ware card will let you organize volumes as you wish.  E.g.,
  /dev/sda is my RAID-1 "System"
  /dev/sdb is my RAID-5 "Data"

I then slice (partition) and mount each.
  /, swap, /tmp, /var, /var/log, etc... go on the former
  /srv, /home/*, etc... go on the latter

I'm also using LVM2, taking snapshots, etc...  LVM2 seems to be fine at
doing this, as long as you don't do 2 operations at once.  E.g., don't
snapshot when you resize, etc...  It's another reason I don't use LVM/MD
software RAID (i.e., stick with hardware), because it tends to get the
LVM into a race condition.

BTW, I have even totally removed /dev/sdb, physically the drives, and
the rebuilt it, and then re-sliced (re-partitioned) it and then mounted
it anew -- with_out_ rebooting.

> The root & swap are on separate drives.

I put all of them in /dev/sda.  3Ware does read interleaving, meaning it
will grab data in reads from the disks independently.

> The RAID-5 is only for the data which must live.

And that's what I do.

> Reinstalling the OS is child's play next to recreating 
> the data (which can be done but is hideous to do, and I have to recreate 
> about half of it because of the double drive failure).

That's a good strategy.
I also use revision control on all configuration files.

> The first step in my research was to refamiliarize myself with the RAID 
> level definitions.  Six looked nice, but I've never seen its support in 
> any of the cards I've been looking at, nor in Linux's Software RAID 
> HowTo.  So it's just a theoretical thing to me at this time.

RAID-6 is in Linux MD now.
I haven't personally used any cards offering it.

> Hmm, now you've got me leaning back the other way, because the file 
> server does create a single point of failure, and I'm trying to minimize 
> SPOFs (the reason I have 2 duplicators to begin with!).  I could put a 
> 7506-4LP or a 9800S-4LP in each system with 3 250G disks in RAID-5, 
> mirroring to each other nightly.  That'll set me back about $800 or so a 
> system, but that's within my budget.

It's up to you.

-- 
Bryan J. Smith                                    b.j.smith at ieee.org 
-------------------------------------------------------------------- 
Subtotal Cost of Ownership (SCO) for Windows being less than Linux
Total Cost of Ownership (TCO) assumes experts for the former, costly
retraining for the latter, omitted "software assurance" costs in 
compatible desktop OS/apps for the former, no free/legacy reuse for
latter, and no basic security, patch or downtime comparison at all.