RAID 5 with 3x WDC Black 4TB

[davidst99]

Hi,

I have three WDC Black 4TB drives. I would like to put them in RAID 5. I been reading a lot of reviews that are very negative to RAID 5. Is it worth buying another drive and using RAID 10 or is RAID 5 pretty safe? Thanks.

David

 

[nk215]

If you look you'll always find negative review on just about anything. The vast majority of small and medium businesses use RAID5 wo real issue. RAID 5 is fine for a smaller array. More than 10 disks ten you should use something with more redundancy.

The key is backup and use common sense. Incase of a HD failure - if you are not pressed for up time - backup and re-create the array from scratch (vs rebuild). Rebuild the array for a HD failure will take significantly longer than backup and recreate from scratch.

 

[Red Squirrel]

Raid 5 is fine, it's just that there's a bit more risk because you can only lose 1 drive and during the rebuild process there's a slightly higher chance of losing another drive if say, you got a bad batch so they're all slowly dying. With raid 10 you can potentially lose more drives but it does depend which ones. I think the rebuild time is also slightly faster, and performance is also much better.

Personally I would do raid 10, but there's not really anything wrong with raid 5. One nice thing about raid 5 is you can expand by adding 1 drive at a time and it cost less per TB since you only lose 1 drive worth of space not half.

I have a 8 drive raid 5 with 1TB WD blacks and it's been solid, though I find it slow compared to the raid 10 arrays I have. I want to retire it though simply because I can get more performance and space if I use the slots to make a raid 10 with larger drives.

 

[bunnyfubbles]

It would be helpful to know what kind of hardware/software you're working with, and how you intend to utilize the array.

 

[Frost_WD]

[FONT=Times New Roman, serif]Hi davidst99,[/FONT]


[FONT=Times New Roman, serif]Generally, I agree with the guys above, RAID 5 should be fine, but providing more information as to what do you plan to use your system for would be helpful. As @Red_Squirrel suggested with RAID 10 you would get better performance at the price of storage space as it uses two drives for logical discs. It also provides better redundancy for that reason. RAID 5 use one disc for redundancy and the chance of data loss due to hardware failure is slightly higher as you could have two drives fail on you, but that is unlikely.[/FONT]
[FONT=Times New Roman, serif]I would, however, add that the WD Black is a performance orientated drive and is great for gaming and demanding applications, but it is not developed for RAID arrays. With that in mind I would suggest considering the WD Red series. WD Red is developed for the demanding, 24/7 conditions of NAS environments. They have features such as NASware 3.0, TLER which allows for error recovery and prevents drives from being dropped out of the RAID and lower operating temperature. Here is a link: http://products.wdc.com/support/kb.ashx?id=s0fZjj [/FONT]


[FONT=Times New Roman, serif]Keep me posted,[/FONT]
[FONT=Times New Roman, serif]Frost_WD[/FONT]

 

[Essence_of_War]

I think the rebuild time is also slightly faster, and performance is also much better.

The rebuild time for mirrors vs. distributed parity should be quite a bit faster. Read performance is probably comparable, but depending on the raid implementation, write performance should be faster too.

 

[bunnyfubbles]

I would, however, add that the WD Black is a performance orientated drive and is great for gaming and demanding applications, but it is not developed for RAID arrays. With that in mind I would suggest considering the WD Red series. WD Red is developed for the demanding, 24/7 conditions of NAS environments. They have features such as NASware 3.0, TLER which allows for error recovery and prevents drives from being dropped out of the RAID and lower operating temperature. Here is a link: http://products.wdc.com/support/kb.ashx?id=s0fZjj

and this is why we should find out what the OP is planning to use his drives for. While its true that WD Reds are designed to be used in RAID, they're also designed to be used in a NAS where the bottleneck is likely to be the network connection (i.e. 1Gb speeds or just over 100MB/sec reads/writes) and thus the drives are based off of slower 5K RPM designs.

because of that, if the OP want to use this array as part of his system he'll see a lot more performance with Blacks than with Reds. And if he's really worried about getting a drive optimized for RAID, there are 7200 RPM options that are better than the Reds (albeit, slower than the Blacks), the HGST Deskstar NAS drive or even the newer 4TB Seagate options (in particular, the ST4000DX000 model for 7200RPM) are looking like they're going to be viable options with very low failure rates being reported from Backblaze

Now while I don't think Blacks are particularly good value, if you want the performance they're hard to beat. On the other hand Reds just don't offer much value no matter how you look at it. They're not the most reliable, performance is average, and their feature-set isn't unique; its main advantage is WD's brilliant color coding (i.e. branding/marketing advantage) has made it easier for users to just accept how the drive should be used and thus gives them a heightened sense of peace of mind that they have the right product for the task without thinking about it too much. Its not that they're bad drives, they're just not particularly exceptional for how much they go for.

 

[Emulex]

I'd avoid raid-5 and avoid non-tler drives for raid-protection in general. The responsibility of raid-5 is too much when a cold/hard reset would cause a full-rescan of the raid with potential for dropping out of the raid during that lengthy process.

 

[Frost_WD]

Hi guys,


@bunnyfubbles As you pointed out the Op has to decide, and as I have posted above, if he/she provides more information it would be helpful. It all depends on what the OP is looking for, if they require performance in the array they could go with the WD Black, however, that could lead to compatibility problems and as the WD Black does not have TLER drop outs are possible (@Emulex pointed that out quite well) . With that is mind if the OP needs performance they could even consider the WD Red Pro. Those drives have all the advantages of the Red series and have great performance. Here is a link: http://products.wdc.com/support/kb.ashx?id=vHto0S. However, they are pricier.


Cheers,
Frost_WD

 

[dorion]

One nice thing about raid 5 is you can expand by adding 1 drive at a time

That's not a standard feature of Raid 5. The data on raid 5 is spread across the disks n-1 parts data, 1 part parity. When you add another drive you have to recalculate this parity.

 

[Jeff7]

That's not a standard feature of Raid 5. The data on raid 5 is spread across the disks n-1 parts data, 1 part parity. When you add another drive you have to recalculate this parity.

Shouldn't that happen automatically though, in the background?
I upgraded my 4x 1TB array to 4x 2TB.
Steps:
- Swap out the drives one at a time. I might have had to run some Initialize tool in the software, I don't remember that part anymore, but recalculating the parity was done automatically, though it does take a few hours.
- Use Acronis Disk Director to resize the existing partitions to use the newly-available space.

It was fairly painless.

The array is vulnerable while it's redoing the parity though, so that's the riskiest part of it. The other risk is those non-recoverable read errors. Drive sizes have been getting bigger, but the read error rate hasn't been keeping pace.



Interesting thing, as I look again at the specsheet:

Normal drive specs say "<1 in 10^14" as the non-recoverable error rate for a consumer-grade drive.
But the specsheet for the enterprise-grade drive says "<10 in 10^16."
Huh.
So...I'm not good with prob&stat.

How does
10-in-10^16
compare to
1-in-1^14
?

Or did they make a typo in the datasheet, and that 10 should be a 1?