Hello,

I bought a HP EliteDesk 800 to try unraid on. I had two spare 1TB 3.5inch drives which i set for my main storage. I also bought a 1TB 2.5inch to act as parity. I do note that one of the drives is showing a SMART error, but as im only evaluating Im not too bothered as the files are backed up elsewhere. Should i be concerened long term with this?

Ive set up some shares and started to put files into them, accessing over my network from different computers.

However, im confused by the information im seeing relating to the array devices -

1. Why is there not an equal split of used space on the array?

2. If disk1 dies, can i expect to fully recover all the information if I install a replacement disk? I just cant get my head around the unequal split of data across the drives.

3. Why is there no used space on the parity drive?

4. How much storage space do i actually have? I was expecting 1TB but it would appear i have 2TB?

With this basic system, which currently is just used to hold photos and documents, would i benefit from fitting a SSD for the cache?

Thanks.

Click on the thumbs down icon to get more information about the error. Depending on what it is it may be of concern or not.

You are likely to get more informed feedback if you attach your system's diagnostics zip file to your next post in this thread.

It is always a good idea to do this to allow us to see the current state of your system and so we can see logs and configuration information (including SMART information for all your drives).

1. This is dependent on which allocation method you have set in your share settings. It’s probably “high water” which will determine how much space is available on each drive and write to that drive until half the available space is used (minimizes unnecessary spin-up of other drives). You can go to the share settings page for one of your shares and click the question mark to see a description of all settings.

2. With one parity disk you have protection for one failed disk. At the risk of over simplifying, the parity disk stores the sum of each bit for all data drives (odd or even). If a disk fails the system will check sum of each bit for the remaining disks and calculate whether the missing bit was a one or zero. This allows the missing drive to be rebuilt one bit at a time.

3. All space is always used on parity.

4. Unraid is not raid. The total storage space will be the sum of all data drives.

Many thanks for the replies.

I attach the diagnostic file in the hope it means something?

The allocation method was indeed "High water". I'm just finding my way around the system, so kept everything with the default settings. At the moment it works fine, but 'll look into the different options later.

Ah, so i was getting confused comparing UnRaid to Raid.

Would i benefit in anyway by adding a SSD drive for cache?

elitedesk-diagnostics-20260505-1356.zip

5 minutes ago, howardb said:

Would i benefit in anyway by adding a SSD drive for cache?

Depends on your use case. It can improve speeds for network file transfers so if you often transfer large files and have to sit and wait for the transfers to complete there would be advantages there. If transfers are automated and run in the background then maybe no advantage. I’m sure there are other uses as well.

Remember that if you’re just using a single disk cache the files on that disk aren’t protected.

16 minutes ago, howardb said:

Would i benefit in anyway by adding a SSD drive for cache?

Ideally, Docker/VM related shares - appdata, domains, system - would have all files on cache or other pool outside the array, so Docker/VM will perform better, and so array disks can spin down since these files are always open.

20 minutes ago, howardb said:

I attach the diagnostic file in the hope it means something?

32 Reported_Uncorrect is the reason for 👎 . Might be OK for now

Click on disk2 to get to its page, then do extended self-test.

I did the extended self-test which returned "Last SMART test result: Completed without error"

Dashboard array section still shows "Array has 1 SMART error. " but i'll live with that for now, whilst i explore UnRaid.

Many thanks to those who have answered my question. Every day is a school day!

3 hours ago, howardb said:

Dashboard array section still shows "Array has 1 SMART error. " but i'll live with that for now, whilst i explore UnRaid.

If you click on the orange thumbs down icon and select the Acknowledge menu option then Unraid will stop alerting unless the value changes.