Hi TrueNAS Experts,
i am planning to build my trueNAS scale server, the configuration is below:
Core i5 4th Generation
16GB DDR3, 128GB SSD for TrueNAS OS and 2 1 TB HDDs.
i will use Raid 1 so total storage is 1 TB and mirror to other disk.
Now consider the situation from this Raid 1 pool, my one of the disk failed. Yes i know if i replace new disk with failed disk, it sync and pool will be active. But my question is , how to access the data from working disk before i replaced new one ? data access is continuously needed and i may not have time to quickly buy & replaced new disk.
All kind of help and suggestion appreciated 
.
Thank you
-Jiggi
The same way you accessed it before the drive failed. The array keeps working when one disk fails; that’s kind of the point of RAID.
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Thank you Dan, i have played with all NAS features on VirtualVM 
Now as a home NAS and limited budget , again i am confusing to choose disks.
buy two WD/Seagate desktop HDDs (in budget) OR
buy 1 desktop and 1 NAS HDD (budget + extra ) OR
buy 2 NAS HDDs (al most out of budget)
???
Even i am planning to down Home NAS at 12AM night daily. and up in morning.
Is it recommended ?
I really appreciate your suggestion / comment as per your experience.
Thank you
Is the NAS your only source of storage for your data? Do you have a backup of your data elsewhere?
You listed 1TB disks in your first post above. Is that the size you were planning on using? Why are the drives so small? At that price point, a SATA SSD is very close to size and price of a HD. Maybe plan on buying larger HD. The other problem with the small drives is you are trying to keep the pool below 80% capacity for ZFS. It’s 50% if using it for block storage
The important issue is getting disks that use CMR and not SMR. Almost all NAS drives are CMR types. Desktop drives could be either (CMR Conventional Magnetic Recording, SMR Shingled Magnetic Recording)
One option, if you have data backed up elsewhere, is buy 1 NAS hard drive now and create a single stripped pool. When you can afford the second NAS hard drive, you add that to your pool as a mirror to the first drive. You want to make sure it is added as a Mirror and not as a second VDEV. You should still have your data backed up elsewhere though.
SMR vs CMR ServeTheHome
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Arguable if it is recommended - there is debate on if the power savings are worth the theoretical ‘cost’ of your hard drives spinning up/down which can cause more stress on the drive heads &, in theory, possibly, lead to premature death of an HDD. Which replacing could be more cost than saved on electricity.
I don’t think there have been enough studies to go either way on it. If you go SSDs, then I’d argue it is nearly without any additional risk.
IMO, if you can - budget a bit more for the disks… I’d also argue that with only 1 drive of redundancy, having a cold spare (drive that isn’t in use, but is ready to replace a failing drive) is always a good idea.
Maybe consider something like the following (or whatever local options are available):
Barky is on the money with making sure drives are CMR (otherwise, you’ll have a very bad time). Also I like his idea of even considering SSDs, especially if this is going to be a WORM pool.