Five Drives for Raid-5

[igloo15]

I am building a freenas system with unraid basically a raid-5 array. Orignally was going to use
Western Digital Caviar Black 750gb

Then I read about them having raid issues and dropping from raids. Also I realized that I might need more space than 3tb so I got to wondering what drives are good for raids. I might end up going with the 1tb version of the above drive but I wanted to now what people's experience are with Western digital dropping out of raids?

 

[VirtualLarry]

I don't know what drives are good for RAIDs. It seems that nearly every desktop drive is prone to dropping out of RAID 5 arrays. At least, I've read about problems with the Seagate 7200.11 in raid arrays, and I had issues in the past with WD 320GB SATA drives in a 4-drive RAID5. However, their replacement, four 500GB WD SATA drives, seemed to work fine.

 

[Emulex]

wd re3 or re4
spinpoint "RAID"
barracuda "ES" or "NS" enterprise and constellation class
hitachi enterprise "starts with E"

make sure you never crash hard reset or cut power - separate storage from other tasks that might fault the system.

 

[pjkenned]

I don't know what drives are good for RAIDs. It seems that nearly every desktop drive is prone to dropping out of RAID 5 arrays. At least, I've read about problems with the Seagate 7200.11 in raid arrays, and I had issues in the past with WD 320GB SATA drives in a 4-drive RAID5. However, their replacement, four 500GB WD SATA drives, seemed to work fine.

I've been running over a dozen 7200.11 drives in raid 6 for the past year on an Adaptec 31605 and have never seen one dropout.

Also, I've found software raid to be much more friendly to consumer drives.

To the OP: Why 750GB drives? My advice having built a 18TB+ system last year and moving to a 30+ TB system this year is to buy big drives. Less drives is lower failure rate and usually lower power consumption.

 

[igloo15]

I am using ZFS and power backup so hopefully no fault errors from crashing or improper shutdown. Also its a software raid so maybe it will not dropout as opposed to a hardware raid.

I am going with more drives in lower capacities so that I can more easily upgrade in the future. Upgrading 5 drives from 750gb to 2tb is easy and gives me more capacity in the long run.

At the same time if I were to get 3 drives of 2tb than what would my upgrade path be. 4tb drives which don't even exist? Plus increasing the number of drives in a RAID is very difficult ie going from 3 drives to 5 drives.

Finally I have a budget, I would want to go 3 drives 2tb but I just don't have enough money.

 

[imagoon]

I am using ZFS and power backup so hopefully no fault errors from crashing or improper shutdown. Also its a software raid so maybe it will not dropout as opposed to a hardware raid.

I am going with more drives in lower capacities so that I can more easily upgrade in the future. Upgrading 5 drives from 750gb to 2tb is easy and gives me more capacity in the long run.

At the same time if I were to get 3 drives of 2tb than what would my upgrade path be. 4tb drives which don't even exist? Plus increasing the number of drives in a RAID is very difficult ie going from 3 drives to 5 drives.

Finally I have a budget, I would want to go 3 drives 2tb but I just don't have enough money.

Emulex wasn't talking about a file system issue but a RAID rebuild issue. With the power cut off mid write there is potential for a cluster to not add up correctly and not be recoverable. Some RAID systems handle that issue better than others. During a array check the controller could decide to just drop the array and leave you piecing the disks back together.

 

[igloo15]

Yes but that is the draw of ZFS software raid it is able to prevent these types of errors.

 

[Emulex]

if the raid is not cleanly shutdown it will attempt to scan or rebuild it. during this time if another drive fails (or two in raid-6 or more with raid-0+1) then you have a situation

the problem can be tweaked with software raid i'm sure. but the real issue is when you have that raid under load and its rescanning you are pushing timing even tighter.

you realize to rebuild/rescan a 6TB raid-5 could take days. thats a huge open window for failure.

Raid-0+1 is nice because it basically mirrors every 2 drives then rolls them all together with a big stripe. this gives you far more protection without incurring the massive cost of reading/writing/compute crc.

given that most people use intel matrix/nforce raid - i am speaking in that generalization. software raid can have some advantages - definitely if you can tweak your drivers and the software raid to be more tolerant - not everyone knows gcc

real raid controllers are very intolerant unless tweaked by someone of consumer drives as well. dell and hp even push their own "DRIVE" firmware to match their controllers best.

sata drives and raid just make me cringe. just an accident waiting to happen but we're not all rich.

 

[igloo15]

Unfortunately I am not an expert at ZFS's unraid or raid-z implementation. From what I have read though it uses transactions and small partitions so a failure would only effect a small portion and not the entire raid. When it goes to rebuild it only builds the small partition and does not have to rebuild/rescan the entire raid.

 

[Emulex]

yeah raid-z looks cool and smart. are you using opensolaris? or is there a windows based solution for this?

i wonder how well/poorly it retains ntfs permissions? thats my main problem - i need perms to be persistent across a domain and most anything other than ntfs doesn't really do a good job in that area.

 

[Rifter]

Im running 3 1.5TB seagate LP's in Linux software RAID 5 and have not had any issues, even when i was having video card issues and my linux server was hardlocking and required me to power off then back on they gave me no hassel, just rebuilt on bootup and back to normal. Now that i have a Nvidia card in the server its been running a few months no issues.

 

[pjkenned]

I played around with Raid-Z2 in FreeNAS. I'm not a huge fan just because it doesn't have OCE. It would be pretty cool save that one feature.

 

[igloo15]

Yeah I am going to try and make a freenas box with 5 1tb drives hopefully it works out.

Might I ask what is OCE? From what I can tell of Freenas it seems to have all the features I want so don't think it will be an issue for me.

 

[RebateMonger]

Might I ask what is OCE? From what I can tell of Freenas it seems to have all the features I want so don't think it will be an issue for me.

Online Capacity Expansion. The ability to add additional disks to a RAID array while your system is running.

 

[Emulex]

offline capacity expansion is cool though?

 

[pjkenned]

Well even offline Raid-Z2 was not fun since you have to add sets of drives. Granted, I do that anyway to some extent, however I didn't like the idea of spending $800+ each time I wanted more capacity (6x 2TB drives or 8x 1.5TB drives would basically be what I'd use).

Then again, there are benefits to Raid-Z2 and sub 10TB adding drives would be pretty easy.

 

[ViviTheMage]

I have 6 of these in a raid 5 :

ST31000528AS

works fine SO far

 

[Night201]

Have you checked out Unraid?
http://lime-technology.com/

 

[Emulex]

raid-z on freenas seems to be a good solution. i wonder if it is an option with openfiler. openfiler has a better iscsi implementation imo.

neither freenas nor openfiler are very tolerant of consumer drive errors

imo they should reserve say 10% for bad sectors and handle that at the filesystem level as well as at the raid-z level to make a better raid solution.

 

[TheMouse]

Have you checked out Unraid?
http://lime-technology.com/

Now this is interesting. I use a Netgear ReadyNAS (Expandable RAID 6 configuration)... I like the simpler technology of Unraid.

 

[igloo15]

Interesting didn't know there was a company that built unraid systems. Anyways looks like it will still be cheaper to build my system out of spare parts from my old computer than buying one.

 

[Night201]

Interesting didn't know there was a company that built unraid systems. Anyways looks like it will still be cheaper to build my system out of spare parts from my old computer than buying one.

This company is the one that actually makes it. They sell pre-built systems, but anyone that is computer savvy and put together systems can easily do so. It's very easy and straightforward. Quick too!

 

[Evadman]

I have several RAID5 arrays built out of a multitude of different disks (probably used more than 100 different disks in the last 2 years, and many many more over the last ~10 years) and I have found that until the recent .11 version of Seagate, all manufacturers failed at the same rate. I have found that the .11 seagate's have has substantially more issues.

I am currently using 20 Seagate ST31500341AS drives in a RAID 60 array on an adaptec 52445, and a mix of 12 different manufacturer 750 gb drives in a RAID5 array on a adaptec 31205 for backup.

 

[pjkenned]

I have found that until the recent .11 version of Seagate, all manufacturers failed at the same rate. I have found that the .11 seagate's have has substantially more issues.

Were they all firmware upgraded? I had a DOA and one firmware death in the first week of buying over a dozen. Since then all of the 7200.11's have been working fine on the Adaptec 31605 in raid 6. Just bought 8x WD 1.5 greens and another 8 hitachi drives (2x 1TB 6x 2TB) and the hitachi were all fine whilst the WD Greens saw 3/8 die in 14 days. I'm probably going to JBOD the greens for backup now and buy more Hitachi's.

 

[Emulex]

most of the ones i had problems with just needed a good long burn to remap sectors. a secure sector delete does the trick