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Old 08-29-2009, 12:03 PM   #1
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Chosing a RAID for NAS: HW Raid, FRAID, SW Raid

Hello out there,

I just cannot get my head around this and would be grateful for some input!

My intention: to build a NAS (@home) which does the following:
  • provide me with my data anywhere and with any protocol I want
  • provide data security (this is actually most important to me)

My system so far:
  • Via Epia SN (which has a VT8251 Southbridge, thus a raid controller onboard of which I do not know if it is one of the dreaded fake raid controler)
  • 4x1TB hdd
  • FreeBSD based OS (FreeNas) for now
  • OS installed on a separate drive (CF card) - no need to boot from raid

The system is up and running, I just cannot decide on what to do with my hdds

First option:
Have the onboard raid controller create a raid5 and let the OS use the thus created "raid drive". This would be the obvious choice, if it weren't for this one major disadvantage: I did the following: I set up the system in this way and removed a drive. No data loss, system working fine, BUT the raid bios setup does not include a "rebuild" feature. These features are part of Via's "v-raid" driver, which is not available for FreeBSD. Thus, plugging the drive back in will not regenerate the raid. I would have to copy everything off the raid, delete and then recreate the raid and copy everything back on it...not very convenient. Also, what happens when the board goes done?

Second option:
Software raid. Let the onboard controller not do anything. Have the OS use all four hdds to create a software raid5. Now, performance-wise, there seems to be debate whether this is a real disadvantage over "cheap" raid controllers (right?). Within this option, I'd have all the raid operations available. But, what happens in the case of a mainboard or OS-disk failure? Will a newly installed OS be able to recognize the raid?

Third option:
Get a dedicated hardware raid controller. Well, I do want data security and a decent performance, but I am not running any public service. Given the price of my system so far (600) spending another 300 on a raid controller would be rather heavy. But then again, if that's my only option to data security, that's what I'd have to do.

Well, again, I would be grateful for any input! Thanks!
Old 08-29-2009, 10:47 PM   #2
Registered: Jun 2009
Location: Penang, Malaysia
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On-board controller-less raid on most motherboards are usually no better performing than a normal OS based software raid. (depends on the OS though)

I'm never used FreeNAS, but on Linux the software raid is quite reliable. OS failure or disk failure is usually not a problem as the RAID information is stored on the member disks themselves. On OS failure, you may just need to reactivate the array after OS reload. For disk failure, just swap out the disk & it should rebuild.

Hardware raid is the best option no doubt. But as u noticed, the price may be a bit steep. Cheap cards often don't support anything beyond raid 0 & 1. Something that supports raid 5 will cost quite a fair bit.
Old 08-29-2009, 11:43 PM   #3
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I think you could get a Raid card for cheaper then 300€, An LSI SAS3041E could proably run under 200€ I reckon and those are pretty decent raid cards, they won't do Raid 5 from memory but do, do raids 0, 1 and 10.

However if this is personal only and not buisness supporting in anyway I would suggest trying software raid, this should give you better flexability then the embedded, then if that just doesn't seem to cut it, get a proper hardware raid card later if you believe the H/W raid will fix the issues you do have.


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