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Forum Discussion
TMcL
Jun 29, 2019Tutor
ReadyNas Pro 4 expansion
I'd like to be sure I understand properly and will take the correct steps.
ReadyNas Pro 4 XRAID2
Raidiator -x86 4.2.31
Raid Level X-RAID2 4 disks
(my accessing units are mostly windows 7 & 10)
I thought I set it up with redudundancy because even though I had 4x1T disks, I only ever had about 2T. So I thought that my disks were duplicated.
But now I have the error below. Does it just mean I have to replace disk 1 and then i will get my redundancy back?
Also, I am hitting my storage limit. Can I replace with (supported) 4x3T drives (one by one starting with goner)? I THINK that will keep me under the 8T max expansion limit.
I do have data backed up on Carbonite and I've tested the recovery (different saga).
But that process is slow so I'd rather do the hot swap route if possible.
TIA!
T
Configuration: RAID Level X-RAID2, 4 disks
Status: Not redundant. A disk failure will render this volume dead.
RAID Disks:
Ch 1 : WDC WD1002FBYS-02A6B0 [931 GB] had not-green dot next to it
Ch 2 : WDC WD1002FBYS-02A6B0 [931 GB] 927 GB allocated green dot
Ch 3 : WDC WD1002FBYS-02A6B0 [931 GB] 927 GB allocated green dot
Ch 4 : WDC WD1002FBYS-02A6B0 [931 GB] 927 GB allocated green dot
TMcL wrote:
Thank you! I feel reassured about the replacement.
I had read ages ago about teh parity but forgotten - or as i say I must have slept since then. Thank you for explaining it in more detail. Pretty neat.
One follow up regarding replacement drive size.
I found in another post - by you I believe - the concept of
""sum the disks and subtract the largest". " to find storage space in Raid 5.
Using this format, - again my orig confi is 4x1TB
Can I use 4x4TB replacements and still be under the 8 TB expansion limit.?
The growth would be 9 TB (since your starting point was a 3 TB volume, and 4x4TB would give you a 12 TB volume). 9 TB is ~8.2 TiB, which unfortunately that is just over the limit.
6 Replies
Replies have been turned off for this discussion
- StephenBGuru - Experienced User
TMcL wrote:
I thought I set it up with redudundancy because even though I had 4x1T disks, I only ever had about 2T. So I thought that my disks were duplicated.
But now I have the error below. Does it just mean I have to replace disk 1 and then i will get my redundancy back?
Configuration: RAID Level X-RAID2, 4 disks
Status: Not redundant. A disk failure will render this volume dead.
RAID Disks:
Ch 1 : WDC WD1002FBYS-02A6B0 [931 GB] had not-green dot next to it
Replacing disk 1 will restore your redundancy.
4x1TB X-RAID2 uses standard RAID-5. So the capacity would be 3 TB. However, the Web UI actually reports the size in TiB (1024*1024*1024*1024 byte = 1 TiB) - so it should report ~2.7 TiB.
FWIW, the disks aren't duplicated - the redundancy is provided in a different way. The disks are organized into data blocks and parity blocks - for example you'd have data block A on disk 1, data block B on disk 2, data block C on disk 3, and parity block P on disk 4.
The partity block P is computed from A, B, C.
P=A+B+C
The actual partity block construction doesn't use addition (it uses XOR), but you can think of it as addition. Every time you update one of the data blocks, the NAS recomputes the associated parity block.
Then if a disk fails or is replaced, you can reconstruct the missing block using one of the equations below:
A=B+C-P B=A+C-P C=A+B-P P=A+B+C
In this example the first equation would apply. Note that the parity block isn't always on disk 4, the pattern is rotated so that some partity blocks are on each disk.
TMcL wrote:
Also, I am hitting my storage limit. Can I replace with (supported) 4x3T drives (one by one starting with goner)? I THINK that will keep me under the 8T max expansion limit.
You should be fine. 4x3TB gives you a 9 TB volume (~8.2 TiB). So even if you started with a single 1 TB drive you'd still be under the 8 TiB expansion limit (expanding about ~6.4 TiB ).
- TMcLTutor
Thank you! I feel reassured about the replacement.
I had read ages ago about teh parity but forgotten - or as i say I must have slept since then. Thank you for explaining it in more detail. Pretty neat.
One follow up regarding replacement drive size.
I found in another post - by you I believe - the concept of
""sum the disks and subtract the largest". " to find storage space in Raid 5.
Using this format, - again my orig confi is 4x1TB - 3TB
Can I use 4x4TB replacements and still be under the 8 TB expansion limit.?
(4x4)-4= 12 and 12 is 8 larger than original 4
Thank you again!
T
- StephenBGuru - Experienced User
TMcL wrote:
Thank you! I feel reassured about the replacement.
I had read ages ago about teh parity but forgotten - or as i say I must have slept since then. Thank you for explaining it in more detail. Pretty neat.
One follow up regarding replacement drive size.
I found in another post - by you I believe - the concept of
""sum the disks and subtract the largest". " to find storage space in Raid 5.
Using this format, - again my orig confi is 4x1TB
Can I use 4x4TB replacements and still be under the 8 TB expansion limit.?
The growth would be 9 TB (since your starting point was a 3 TB volume, and 4x4TB would give you a 12 TB volume). 9 TB is ~8.2 TiB, which unfortunately that is just over the limit.
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