Start with dual parity?


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I will be building my first UnRAID server in a couple weeks (migrating from Windows) and I have some questions about how to setup the array. I plan to have two parity drives. I have nine WD Red drives available. ( some 2TB and some 4TB)  Most are 2-3 years old but two are brand new in the package. Assuming they all pass preclear, would it be faster to start with two parity drives? Or add the second parity drive after all the data has been migrated? (since it will likely take several days at least for all the data to be migrated and each drive run through pre clear) Or does it not really matter? Is there anything else I should consider when deciding to start with two parity drives or add the second parity drive after the data is migrated?

 

For the data migration I was planning to create the array with one data drive (4TB) and one or two parity drives. (4TB) Then slide one of my other drives (NTFS) into the server. Using the "unassigned drives" plugin and the Krusader docker I would then copy the data to the array. Once the copy is complete, I would pre clear the drive. Once pre clear is complete, I would format the drive and add it to the array. Then I would repeat this process until all my drives have been added to the array. Does this process sound correct? Is there a better way to do it?

Thanks.

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Hello,

There are thing to clarify before any proper advice.

 

1. You talk about several arrays, one with single parity and the other with double parity.

This is not yet possible with Unraid. You can have one Parity protected Array and one disk pool with various levels of RAID. If you start with 6.9 beta instead of 6.8.3 stable you can then have several pools. My advice would be to go with the last available 6.9 beta as it offers other benefits.

 

2. How do you plan to make the initial data transfer ? Do you have another server or is it external drives, drives from your main PC, etc. ?

Do you plan to use drives that you have laying around or take the drives that have your data and add them to Unraid as soon as the data has been transferred ?

 

I am asking this because it is generally advised not to use transfer cache or Parity for the initial transfer as it generally slows down the process. You are not mentioning the former, only the later.

This is faster, but by definition, no Parity = no Redundancy. This is acceptable you you still have your data elsewhere while there is no parity.

 

3. Can you tell us about the hardware you plan on using ?

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Thank you for your response! I hope I can explain it more clearly.

 

I currently have a Windows 7 server. I'm running "FlexRAID". FlexRaid is no longer supported, so I'm moving to UnRAID. The plan is to "Gut" my Windows server as the MB and CPU are very old. Then rebuild the server using an AMD Ryzen 5 3600 six core CPU and an Asrock X570 Pro4 MB. (both of which I already own) Also I will using a SAS2LP-MV8 SAS controller. (repurposing from current server) I will also be repurposing my nine WD red hard drives. Six of which have data on them and three do not. (all are NTFS) My understanding is UnRAID 6.9 Beta is needed to support the new hardware I plan to use. So I'm planning on using UnRAID 6.9 beta 35. Also from what I understand the minimum number of drives in an UnRAID array is two. One data drive and one parity drive. I plan on building one array in total and eventually using all nine of my drives. I plan on having two parity drives in my one array. My question is, would it be faster to start with two parity drives in my one array? Or add the second parity drive after all the data has been migrated? (since it will likely take several days at least for all the data to be migrated and each drive run through pre clear) Or does it not really matter? Is there anything else I should consider when deciding to start with two parity drives or add the second parity drive after the data is migrated?

 

"For the data migration I was planning to start by creating the array (same one array as mentioned above) with one data drive (4TB) and one or two parity drives. (4TB) (to be determined by the answer of question in above paragraph) Then slide one of my other drives (NTFS) into the server. Using the "unassigned drives" plugin and the Krusader docker I would then copy the data to the array. Once the copy is complete, I would pre clear the drive. Once pre clear is complete, I would format the drive and add it to the array. Then I would repeat this process until all my drives have been added to the one array. Does this process sound correct? Is there a better way to do it?

Thanks."

 

Let me know if that clarifies it for you. Or if you have more questions. Thanks again!

 

 

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Parity is not mandatory, so you can perfectly start with a 1 drive Array (with no Parity obvously :D ) or 2 Data drives and add Parity later.

 

What I would do is install Parity as late as possible to speed up data transfer.

When to do that would depend on the number of drives of the largest size (I guess 4TB) and if they are empty or full at the moment.

 

Regarding the SAS2LP-MV8, I think that this board is not recommended, that needs to be confirmed by someone with more experience in SAS addon board.

Edited by ChatNoir
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Ok, so I have three 4TB drives with no data. Two 4TB with data and four 2TB drives with data. If I understand what you are saying, whether I start with one parity drive or two parity drives it makes no difference. Adding all the data drives first, then adding the parity drives last would be fastest method for creating my array and migrating my data? Even though I will be preclearing my drives before they are added to the array, should a drive fail after it gets added to the array there is still a small chance of loosing all my data on the drives that are already in the array? (with no parity drive) Or just the data from the failed drive?

 

Does my method for migrating my data sound correct? (see previous post)

 

Thanks!

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2 hours ago, nettech_gt said:

SAS2LP-MV8 SAS

YMMV.  Some users have no problems with Marvel based controllers, others have nothing but problems.  You will always have the best luck with LSI based (say a 9201 or Dell Perc H200) flashed into IT mode.  You can find them very reasonable on ebay as server pulls (but beware of ones bought from China as the odds are good that they're counterfeit

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So, to recap, your goal is to:

  • transfer all data
  • end up with a double parity
  • preclear all drives before adding them to the array (more on this at the end*)
  • transfer all drives
  • do it as quickly and safely as possible

You have 3 empty 4TB, 2 full 4TB & 4 full 2TB.

 

If that was me, I would:

  1. preclear all 3 new 4TB drives
  2. once done, add 2 as Data drives, 1 as Parity
  3. copy the content of your 2 full 4TB drives to the Array
  4. Preclear the 2 old 4TB*
  5. Add them to the Array (1 as Data, one as Parity)
  6. copy the content of 2 2TB drives to the Array
  7. Preclear the 2 2TB*
  8. Add them to the Array
  9. copy the content of 2 last 2TB drives to the Array
  10. Preclear the last 2 2TB*
  11. Add them to the Array

Of course, that's only my opinion, with my One server build less than 6 monts ago. ;) 

 

Additional notes:

  1. Preclear is generally used to detect early failures on NEW drives, if your old drives are OK, I am not sure the steps 4/7/10 are necessary, maybe an Extended Smart test can be enough ? If someone else has an opinion on that...
  2. If you prefer having only NEW drives as Parity, you will have to change things a little. However, the first 4TB drives you will replace will be the Parity ones as no data drive can be larger than any parity drive, so if your old 4TB are recent enough and in good shape, this should not be an issue.
Edited by ChatNoir
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That sounds like a good plan. I'll run a extended SMART test on my old drives and only pre clear the new drives. **Unless anyone else advises against it.** I think I'll hold off on using my SAS2LP-MV8 and avoid any unnecessary issues during the initial setup. The MB I'm using has 8 SATA ports. So I should be able to get away with just using eight drives to start. If I find I'm needing more space, I'll consider trying my SAS2LP-MV8 once 6.9 is out of Beta. Thanks for your help!

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