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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

RAID5 or RAID6?

Matt Doane

Matt Doane

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Hey all,

Just bought a thunderbolt array from macgurus. The unit has eight 2TB drives and can run all kinds of RAID. In the past I've always used RAID5 on smoke/flame systems, but those had much smaller and many more drives. Reading today it seems that many people stopped using RAID5 with bigger capacity drives and opt for RAID6 instead. What do you guys think? 5 with a bit more capacity, or 6 with a bit more security?
 
raid 5 will give you slightly better write performance compared to raid 6.....if you are concerned about security, run a raid 5 plus spare, the only time a raid 5 is in danger is when one of the drives has failed and you have to rebuild...if a drive goes during rebuild you are out of luck....the spare takes care of that....
 
paul schefz said:
raid 5 will give you slightly better write performance compared to raid 6.....if you are concerned about security, run a raid 5 plus spare, the only time a raid 5 is in danger is when one of the drives has failed and you have to rebuild...if a drive goes during rebuild you are out of luck....the spare takes care of that....
Click to expand...

Did you read the article linked to above?

http://www.zdnet.com/blog/storage/why-raid-6-stops-working-in-2019/805

"You have a 62% chance of data loss due to an uncorrectable read error on a 7 drive RAID with one failed disk, assuming a 10^14 read error rate and ~23 billion sectors in 12 TB. Feeling lucky?"
 
joe hedge said:
Did you read the article linked to above?

http://www.zdnet.com/blog/storage/why-raid-6-stops-working-in-2019/805

"You have a 62% chance of data loss due to an uncorrectable read error on a 7 drive RAID with one failed disk, assuming a 10^14 read error rate and ~23 billion sectors in 12 TB. Feeling lucky?"
Click to expand...
i wasn't aware of that article and my head hurts from trying to read it....i also have to say that i have never had a 7 drive array....after 20 years working with computers i know one thing...HDs will fail....so i am assuming nobody really thinks that a raid 5 or 6 or whatever is the definitive answer.....i run raid 5s on my boxes, had one drive fail in 20 years but change my equipment frequently so i never use a drive for longer then 4 or 5 years (at the longest)....the most important back up is off site....i choose to do this with several different online solutions, and yes fios does come in very handy....
 
To my experience, Raid5 is enough. Actually if you choose a Enterprise level Raid case, it almost never fail, but if you choose a common level raid case, it will always fail. Quality is a big issue in raid, I do not know the detail, but that is my experience. Another thing is quality of disks. Anyway, this is video, not realtime bank data, Raid fail is not a big deal, we can always backup everything:).
 
paul schefz said:
raid 5 will give you slightly better write performance compared to raid 6.....if you are concerned about security, run a raid 5 plus spare, the only time a raid 5 is in danger is when one of the drives has failed and you have to rebuild...if a drive goes during rebuild you are out of luck....the spare takes care of that....
Click to expand...

What is the point of having a hot spare and not use Raid 6? That to me sounds silly.
You will have the same amount of drive space usage, and yet without the data backed onto the HOTSPARE, until after you crash.

Bottom Line Raid 6 = Raid 5 + Hotspare Already backedup.
 
Richard Tran said:
What is the point of having a hot spare and not use Raid 6? That to me sounds silly.
You will have the same amount of drive space usage, and yet without the data backed onto the HOTSPARE, until after you crash.

Bottom Line Raid 6 = Raid 5 + Hotspare Already backedup.
Click to expand...
in theory a raid 5 +hotspare is safer then raid 6 while rebuilding and raid 5 will give slightly better performance then raid 6....
raid 10 in my experience does not have any performance advantages over raid 5, uses a lot more disc space and you still have the problem of what happens if a drive fails during rebuild....
like zhang ming said, the most important thing is the quality of the array and the drives....i have never had any problems, raid 5 has always given me the best performance, the most space and since i have several backups, i never bothered with a hot spare....it seems like other people have very strong other opinions about this, i can only speak for myself and my experience...
 
I've got it up and running with RAID 6. Write speed is fast, but the read speed seems a bit low to me.

N0Cq6.png
 
Well, now it's reading better when I make the stress test larger. I guess that's more accurate.

mqRP2.png
 
Matt Doane said:
Hey all,

Just bought a thunderbolt array from macgurus. The unit has eight 2TB drives and can run all kinds of RAID. In the past I've always used RAID5 on smoke/flame systems, but those had much smaller and many more drives. Reading today it seems that many people stopped using RAID5 with bigger capacity drives and opt for RAID6 instead. What do you guys think? 5 with a bit more capacity, or 6 with a bit more security?
Click to expand...

I would look into having a solid process of backing up all your data. RAID5 and RAID6 both have their pro's & con's. Data loss is absolute nightmare.
 
For piece of mind, would suggest purchasing Western Digital RE4 drives.

They are designed to work in RAID arrays so that they do NOT attempt heroic correction for any sectors.

They are design to fail and map out marginal sectors (the opposite of 'normal' drives).

They also live a long time. I've yet to have one die - and it's a very, very rare even to even see a sector get mapped out. It's been a few years for me - and I have a lot of RAID arrays.

You might also consider RAID cards that contain a BBU unit to deal with your power supply or UPS failure.

The top ones also handle the tricky issue of the cache on the hard drive itself. Just because it's written out the data to the hard drive, doesn't mean it's on the disk yet, it could be in cache. I've been quite happy with older 3ware (now owned by LSI) cards that have been 'battle tested', so to speak. I'd rather be safe and sure than have the absolute latest and greatest - that has yet to have all the bugs worked out.

And the next most important thing to consider is the power supply.

A failed power supply could easily wipe out 2 drives in an array - so buy the best and buy way more watts than you need.

They will run cooler and be happier.

I'm personally leaning towards Corsair AX1200i (which are I think manufactured by Flextronics).

They have a 7 year warranty, less parts to fail as they are DSP based, totally modular plugs (even the 24 pins), and at 1200 watts, overkill for most situations.

Or play it even safer and buy their older AX1200 units, which are cheaper - but have definitely had all the bugs worked out (the 1200i only came out in Aug 2012).
 
RAID-5 is plenty good unless you have more than 6 drives. Even then, there are advantages and disadvantages. You're not really gaining any extra security by opting for RAID-6. If a drive fails you should be able to recover either way, depending on how the failure occurs. With two drives failing, there's a chance you're going to be OK, but you'll probably suffer some data corruption or loss. 3 or more or a controller failure, you're screwed.

+1 to Les C's suggestion of RE4 drives above, they have yet to let me down. Yes, in all the drives I buy, I have had a couple DOA ones and one failure I can recall clearly, but that's to be expected. They perform great and the 2TB RE4's have had the best reliability (for me) of any drives I've ever used <knock wood>.


My advice here would be to stick with RAID-5 and keep the extra performance. Have a good backup strategy in place and then you don't have to worry so much. If you're trusting a RAID to keep your data safe, you're tempting fate.
 
joe hedge said:
Did you read the article linked to above?

http://www.zdnet.com/blog/storage/why-raid-6-stops-working-in-2019/805

"You have a 62% chance of data loss due to an uncorrectable read error on a 7 drive RAID with one failed disk, assuming a 10^14 read error rate and ~23 billion sectors in 12 TB. Feeling lucky?"
Click to expand...
This assumes the RAID array isn't constantly testing itself.

Good array management software will have an auto-verify mode where you can also set the verify speed to favor 'fastest verify' or 'fastest I/O' (when can be toggled on/off, of course). The software should notice when the array is being used, and avoid verifying during that time.

If all the sectors get tested every few days (or more often if the box is running un-used over night [unless you're doing massive 3d-renders]), there's far less chance (not a zero chance) of more than one drive failing before a rebuild can take place.
 
it get's so lonely in the post production section...
 
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