Areca RAID and data safety

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Cr0n_J0b

n00b
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Dec 19, 2010
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I'm playing around with my new Areca 1260 and I've already hit a data corruption issue. I have an 9 drive raid group (500GB each) that I've carved into a 2TB R5 lun. I presented the LUN to my ESX guest using Raw Device Mapping and all seemed to go pretty well. It's as fast a i need (200MB/s read, 400MB/s write) and that's good enough for me.

So I loaded it up the other day with media files and started to do some editing...again, everything seemed fine. I had to move and reboot the server a couple of times...but everything came up clean, no errors in the RAID terminal.

Today, however, I noticed that half of my data went missing and I got tons of IO errors accessing directories. I ran an fsck and it basically took half of my data out and dumped it into lost+found. that's a bit un-nerving. I have since cleaned it up again and replaced the data, but it got me thinking....

I've set the controller for agressive caching. I basically turned on all of the caching possible, since it's on a UPS and I'm not really worried about a power outage. But now I'm thinking I might back off this.

So what should i leave on and what should I turn off?

(spin-down is also turned on for the disks. That's one thing I definitely want to keep).

thanks
 
So there was no chance of the machine powering off uncleanly?

If not it could be a faulty raid card. I have seen this.
 
It's possible that the system powered off uncleanly. i've been doing lots of testing on it. are there some settings in the RAID card that I should back off of to make sure that even in the event of an unclean shutdown it will still keep working?
 
If you do not have the BBU you need to turn off the write cache. However that will result in very bad write performance but your data will not be at risk.
 
Do you have the Areca battery backup unit? Without the BBU I would not set up the caching.

I've had nothing but trouble trying to use the spin-down features. Especially when using the drives as part of any parity-equipped array (raid 5, 6). There's just too much housekeeping those arrays need to realistically think spinning down drives is going to work.

Combining that with caching without a BBU and that seems like a recipe for disaster to me.

As an aside, nothing seems to really do a decent job of presenting an expandable array with spin-down power management. Shame, really.
 
nothing seems to really do a decent job of presenting an expandable array with spin-down power management. Shame, really.
Click to expand...

If you know what you are doing this can be achieved with linux software raid.
 
drescherjm said:
If you know what you are doing this can be achieved with linux software raid.
Click to expand...

Um, no. Not without a whole lot of hassles. Been there, done that. Not to mention no bare-metal workstation backup/restore. To say nothing of the lack of UI management. Months or years later if a drive dies with WHS it's likely just a matter of clicking through some dialog boxes. With most *nix setups it's a nightmare of shell commands and text files. Great if you're a sysadmin seeking to maintain employment. Bad if you're just a normal person looking for an easy to use, easy to maintain, network appliance.
 
That is why I said if you know what you are doing. I have no hassles at all.

These shell commands are perfectly natural to me and I can easily administer my raid arrays from an ssh connection from across the world via a low bandwith connection.
 
If I know what I'm doing isn't a very good excuse for unfriendly management tools. Hell, I can field dress fresh kill in the forest, but the supermarket makes it a lot less hassle. I don't have to trudge out there at 4 in the morning to lay in wait in order to fix dinner. Same goes for fighting with arcane command line tools.
 
thanks for the responses. I've had mdadm setup for a long time with some of these drives, but I wasn't seeing the performance I expected and it's a REAL pain to pass through disks to ESX client in a raw fashion. I was just hoping for something easy with a raid card that could spin-down and everything would be good. I guess not...

I don't have the battery, but based on this, I definitely will get one this year. They are about $100 right?

thanks
 
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