Replacing a drive that is about to go bad.

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bolter wrote:

I believe that when I formatted the system, I selected flexiRaid which selects its own raid type.

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It's important to know this for certain.  Look at the home screen in the web UI.  If you are in XRAID mode you will see [X-RAID2] after the model number.

 

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bolter wrote:

1st question - Can I just remove the bad drive and replace it with the new one and let it resync?

 

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Yes.  I recommend doing this with the NAS running (hot-swap).  There's no need to format the replacement drive, though you might want to test it with vendor diags in a PC first (lifeguard for western digital, or seatools for seagate). NAS-purposed (e.g., WDC Reds or Seagate Ironwolf) are recommended, as are enterprise-class drives. 

 

I recommend against desktop-class drives (particularly Seagate DMs) even if they are on the compatibility list.  Note that list is quite dated, and many of the drives on it are obsolete - Netgear stopped updating it a long time ago for legacy NAS.

 

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bolter wrote:

 

2nd question - If I replace the 3TB drive with a 4TB one, will this give me more capacity. Or will it only recognise it as a 3TB drive.

 

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You won't get any more capacity. If you are in XRAID, you'll see an increase of 1 TB when you upgrade a second drive.  If you are using flexraid RAID-5, then all drives would need to be upgraded (though you should read through the expansion limits below).

 

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bolter wrote:

 

3rd question - I eventually want to replace all drives with 4TB ones. After replacing the last one, will it recognise them as 4TB drives or still as 3TB drives as originally formatted.

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The expansion will fail.

 

There are two limits to expansion on OS 4.2.x systems.

• The volume cannot be expanded beyond 16 TiB (~17 TB).  This doesn't include redundancy - the rule for capacity is "sum the drives and subtract the largest" for X-RAID-2)
• The volume cannot grow more than 8 TiB over it's initial size.  If you don't recall what this was, you can look in expansion.log.  The info can be a bit hard to follow, but you should be able to see the disks at the last factory install enumerated (with sizes).

Either way (flexraid or xraid), 6x4TB gives you a 20 TB volume size, which is over the limit.

 

If you started with 6x3TB using XRAID, then you should be able to grow to 3x4TB+3xTB, giving you a 17 TB volume.  After that, expansion will fail.  If you are using flexraid, then you simply can't expand any more.

 

The best solution would be to back up all your data, and convert to OS 6.  That requires a factory reset, so it is destructive (hence the need for backup).  It has no known expansion limits.