I am preparing to purchase a 16TB PR100. I understand Raid 1 with 2 drives but don’t understand exactly how it works with 4 drives. How does it pair the drives. Bay 1 to 2 and 3 to 4?
from looking at the user manual for the PR4100 4 bay device it looks like it supports support JBOD, RAID 0, RAID 1, RAID 5, and RAID 10. An explanation of the different RAID configurations can be found in the UM (linked below) on page 54 and 55. I would recommend using RAID 5 for performance and redundancy.
I just purchased the PR100 plus 2 *TB drives. It appears that previously, I didn’t explain myself clearly. I do understand both Raid 1 and Raid 5 to an extent. The reason I will, at the start, run Raid 1 using only 2 8TB drives is that I don’t know how much storage I will need. By using 2 8TB drives running Raid 1, it leaves me the ability to add drives as I need more space. At that time I would migrate to Raid 5. If you purchase a 16TB PR100 preconfigured, it comes with 4x4TB drives which means you will have to pull and replace all those drives to have a larger volume and balanced array. What I was wondering is what Raid 1 does when faced with 4 installed drives as I don’t see any info saying you can’t have 4 drives.
It’d be easier if you used the proper model names: PR2100 or PR4100, it indicates the number of slots.
RAID 1 is mirror mode, providing faster reads and rebuilds… but you get the capacity of a single disk.
RAID 5 is distributed parity mode, providing more capacity.
Note that rebuilding 8 TB of data from RAID 1 to RAID 5 will take about 48 hours.
I’d go for 2 x 8 TB now and buy additional disks when you need them.
The price will be lower by then and 2 drives less uses 10W less electricity.
You also have the faster rebuilds (in case 1 drive dies) and it’s less hassle to recover data from a single RAID1 disk.
I apologize to all for not reading what I wrote. Not being a touch typist sometimes leads to errors which is what happened. The correct term for what I purchased is, “ My Cloud Pro Series PR4100”.
That being said, I am still looking for the answer to my question, " What Raid 1 does when faced with 4 installed drives as I don’t see any info saying you can’t have 4 drives?".
As I said, 4 equal disks in RAID1 gives you the capacity of a single disk, 4 synced copies in total.
Read speeds will be very high (lookup some statistics in the reviews if you want)… but I doubt the rest of your equipment is prepared to handle this.
Almost nobody does this for home use.
Thanks for the info. If I understand correctly, I would have 3 mirrored images of Disk 1. Again, Thanks.
In a way, yes. Anything you read/write happens on 4 disks simultaneously in parallel.
If Disk 1 (/dev/sda) would get corrupted somehow, the RAID software will restore those bytes.
It’s not that everything passes Disk 1 first and to be mirrored by the other disks.
