So i got this new HDD..

[Zenergy]

Sry for the click baity title... lol

 

So i picked up two new HDDs today.  I have 6x3tb (red 5400) with a setup of 2 parity drives.  One drive i purchased is a Samsung 1tb SSD I plan to use for a cache drive.  The second drive a new 4tb Ironwolf (7200) drive.  It was a steal of a deal today on Black Friday so I had to pick it up.   I know it is recommend that my parity drive is larger then my other drives...

 

My question what can i do with the drive?  I would really like to use it as it would be great to have the faster large drive in the array.  don't think i would see any benefit if I replaced one of my parity drives, would i? do both my parity drives need to be the same size?

 

any assistance would be helpful as I still feel like a noob with Unraid. 

 

 

thank you,

 

 

[Squid]

1 hour ago, Zenergy said:

 I know it is recommend that my parity drive is larger then my other drives...

Not recommended, but a requirement.

 

[trurl]

1 hour ago, Zenergy said:

do both my parity drives need to be the same size?

No, but each parity drive must be at least as large as the largest data disk.

 

So, to put it all together, you can use the new disk as one of your parity disks, but you cannot use it as a data disk because neither of your current parity disks are large enough.

[Zenergy]

11 minutes ago, trurl said:

So, to put it all together, you can use the new disk as one of your parity disks, but you cannot use it as a data disk because neither of your current parity disks are large enough.

To be clear...

 

I can replace the two parity disks with the one new 4tb as a system with a single parity drive.  Gaining a single 3tb data drive but loosing a parity drive... I guess that is not a smart idea?

[JonathanM]

Not quite. You could keep dual parity, and add the replaced 3TB parity drive as a data drive, gaining 3TB instead of 4TB of space but keeping dual parity. Or, if you wanted to drop the second parity you could add both old parity drives as data and keep the 4TB as your only parity drive, gaining 6TB of space.

 

If you are confident in the reliability of your current array drives (and if you are not you need to replace any suspect ones) I don't see a need for dual parity for so few drives. You would be better off using that extra parity drive as backup space if you are not already backing up everything.

[trurl]

1 hour ago, Zenergy said:

To be clear...

 

I can replace the two parity disks with the one new 4tb as a system with a single parity drive.  Gaining a single 3tb data drive but loosing a parity drive... I guess that is not a smart idea?

You can have up to 2 parity disks. The parity disks don't have to be the same size as each other. Each parity disk must be at least as large as the largest single data disk.

 

So, you can replace one of your parity disks with the new 4TB and keep the other 3TB parity disk, then use the old 3TB parity disk you replaced as a data disk in a new slot. In that case, all your data disks would still be only 3TB, so each of your parity disk must be at least 3TB. One of the parity could be 4TB and the other parity could be 3TB since one parity disk can be a different size than the other parity disk.

 

If you did want to go to single 4TB parity, then both of the old parity disks could be reused for data.

 

Tell us how you want to proceed. Since you are going to rebuild parity in any case, if you New Config you could add the data disk(s) at the same time and not have to wait for them to clear.

[Zenergy]

Thank you everyone...  I am stuck on the idea of "Raid 5 is dead" which is why I have been running a raid 6 setup on this disks till very recently when I remove QTS on my Qnap and replaced the OS with Unraid.  I am also having trouble wrapping my head around Unraid's way of doing protection so I setup Unraid with 2 parity more out of habit than researching why I should.   Also, the 6x drives are almost 5 years old, it made sense.   

 

I do about 3tb of cloud back up on my family and work data, photos, videos, documents, etc... the rest of the storage is just for plex and other Broll for video editing. I could start over again I still have everything backed up to external USBs.

 

Ultimately I was hoping to add a little more storage to my Qnap by using one of the rear Esata ports till I can save my pennies for a new custom rig I am planning on building.  Moving my video editing to a server storage, etc. 

 

I am flip flopping here on what to do...

[trurl]

2 minutes ago, Zenergy said:

I am also having trouble wrapping my head around Unraid's way of doing protection

Each disk is an independent filesystem, no striping. Each disk can be read separately from the others on any linux. Only disks being accessed need to spin. Each file is completely contained on a single disk, but folders (user shares) can span disks. One or two parity disks provide redundancy. Read speed is only as fast as the single disk being read, and writes are somewhat slower than single disk due to realtime parity updates. Because each disk is independent, different sized disks can be used in the array, and disks can be added or replaced without rebuilding the whole array.

 

Here is the Wiki on how Unraid parity works:

 

https://wiki.unraid.net/UnRAID_6/Overview#Parity-Protected_Array

 

 

[Zenergy]

Is having a larger, fast cache driving a benefit?

[trurl]

There are many ways to use cache. I personally don't bother with using cache to speed up user share writes. Most of my writes are from scheduled backups and queued downloads, so I am not waiting for them to complete anyway.

 

I use cache for my apps (dockers) for better performance, and so the apps won't keep parity and array disks spinning. I don't have any VMs because dockers do everything I want. I also have my Plex docker DVR setup to go to cache for better performance. I either delete those after watching or move them to other user shares long-term.

 

And I have a copy of a subset of my photos and music on cache so other devices on the network can access them without spinning up array disks. I have 2x250GB SSDs as cache, and could probably do with much less.

 

Other people like to cache writes to user shares so they are faster. Cache in that case needs to be large enough to hold those until they can be moved to the array. The default schedule for mover is daily in the middle of the night but that can be changed. In any case, you can't move files from cache to array as fast as you can write to cache. Mover is intended for idle time.

[Zenergy]

2 hours ago, trurl said:

There are many ways to use cache.

Arg, I meant to ask about the Parity drive being larger and faster (7200)…. but that you for the info.. that is something I had not thought about. 

[trurl]

The benefit of having parity larger than any of your data disks is it allows you to replace a data disk with a larger disk. So for example, after you have a 4TB parity, you could replace a 3TB with a 4TB. And 4TB parity will also allow you to add a 4TB disk, whereas a 3TB parity will not allow you to add a 4TB data (your current situation).

 

As for faster, writes always update the data disk to be written, and it updates the parity disk, since parity is realtime. The speed of a write will be limited by the slower of the disks involved. So for example, if you have 5400 parity and 2 data disks, one 5400 and the other 7200, the slower parity won't matter to the 5400 data disk, but it will limit the write speed of the 7200 data disk. So it's best if parity isn't slower than your data disks.

 

Here are some more details about the 2 different ways you can configure parity updates, and the differences between them:

 

https://lime-technology.com/forum/index.php?topic=52122.0