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7200.12 / F3 for desktop RAID 5, or do I need TLER / ERC?

Last response: in Storage
February 13, 2010 8:12:11 AM


New PC up and running (i5, P55, GA-P55-UD3R), and I figure - why not get the data from separate disks to an internal RAID using the onboard Intel RAID?
The only goal is data reliability / longevity.

I currently have some 10EADSs. I know these are not recomended due to both standby issues and lack of TLER (since WD blocked the WDTLER util).

So I understand it is recomeded to use a TLER / ERC drive, but those are double the price! (At least here in Israel). For double the price I can simply buy two disks and have an offline mirror backup.

I see on Seagate's web site that 7200.12 (ST3500418AS) is targeted for "desktop RAID". Obviously, this is not an ERC enabled drive, but a desktop drive. Is that really recomended for desktop RAID? Can I assume by that that ERC / TLER is not a major issue when the Intel chipset RAID used, or am I missing something here?

I also hear great things about the Samsung F3. How does that one compare with the 7200.12 for RAID 5?

Thanks a lot !
February 13, 2010 3:09:51 PM

Samsung f3 and 7200.12 is basically the same
February 13, 2010 6:15:25 PM

Thanks. This I get, but it does not answer my question.

Are those ok for an intel RAID? They do not have an error correction time limitation.

How come the 7200.12 listed as recommended?

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a c 126 G Storage
February 14, 2010 6:39:51 AM

"The only goal is data reliability / longevity"

Is that is true, then why do you consider RAID at all? You should be concentrating on backups if you care about your data. If you care about uptime, then RAID1 or RAID0+1/1+0 is your best bet, but RAID can never replace a backup.

Onboard RAID5 is likely less reliable than a single disk.
February 14, 2010 3:22:17 PM

But is it less reliable than 4 disks?
If I have 4 disks, any one of them can fail. Instead of backing them up individually (which requires 4 backup disks) I figured 1 disk for parity, and I'm done.
Am I wrong?
a c 126 G Storage
February 14, 2010 5:36:35 PM

No, you're right.

The problem is that the RAID5 scheme requires a much more complex design, and many closed-source drivers offer poor support, meaning potential filesystem corruption and low performance. The Intel RAID drivers are actually pretty decent, so RAID5 is still an option assuming you have at least a backup of your most valuable files somewhere else.

Consider your RAID5 as safe as a single disk that can fail. Forget the disk failures - its the havoc after a minor or major disk failure that may destroy your data. For example, after your Windows suddenly froze and you hit reset-button, you see that the RAID array is split into two arrays, and both are unusable. In some cases, the user panics and starts trying things in the RAID BIOS setup like re-creating RAID or deleting the RAID or whatever. This is so dangerous especially with RAID5 because one bad setting and it destroys your data in the process when the parity rebuild starts.

So in short, the RAID drivers may have issues or rough edges causing user error to permanently destroy data that was just temporarily inaccessible. Therefore, the RAID-layer itself is an additional point of failure within your storage-setup. So, using RAID5 both adds risk of failure and reduces risk of failure.

Complicated world, isn't it? ;) 

That's why i say: focus on a backup. It's worth so much more than RAID alone.
February 16, 2010 8:52:33 PM

WOW. Thanks so much for the eye opening response.
OK. I get it. RAID was probably the wrong way. I guess after playing with SCSI RAIDs at work years ago I was too eager to setup one at home.