Remove one SSD from Cache, add another in later?


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I had 2x 500GB SSDs running cache, however one has been failing and blinking offline all the time no matter the backplane slot, so it's going back for RMA.

 

Is there a clean way to remove that one SSD from my cache for now and use the live data left on the other drive w/out rebuilding everything?

 

Then after the new drive arrives am I able to cleanly add it back in? Or would I need to destroy and rebuild the cache each time? 

Trying to find the best way of doing it. Right now the server knows the drive is missing so /var/log is 100% full and I don't know how long it will be before a replacement drive arrives.

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On 8/22/2019 at 9:58 AM, johnnie.black said:

I somehow turned off the "notify me of replies" on this so I missed your (helpful) reply.

 

I had a power failure today and the server shut down cleanly but upon booting back up the server noticed cache1 was gone and it ran a balance on the cache array.

 

Now it thinks it's a 1TB cache for some reason (only ever had 2x 500GB drives in RAID1).

 

My replacement drive should finally be here from Samsung tomorrow, but I'm worried now about simply stopping array and placing this into the cache pool, if it thinks it's 1TB?

 

image.thumb.png.eedf8cad1f2874b10a5e16cdb927d88e.png

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Just now, johnnie.black said:

Because of this bug the missing device isn't being deleted, you need to manually convert metadata to single:

 


btrfs balance start -f -mconvert=single /mnt/cache

 

Then:

 


btrfs device delete missing

 

Before I do this, I want to make sure I need to because that deleted device will be replaced with a new SSD later this evening (when it arrives from Samsung RMA dept). Do I need to still convert to single or can I simply replace the drive later today and then after run btrfs device delete missing? 

 

Thanks in advance. You always come to the rescue when I have issues haha. 

If you have a paypal/venmo I'd happily send you some coffee/pizza money sometime!

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20 minutes ago, johnnie.black said:

Replace the missing device or the one remaining?

I'll be replacing the missing one - so I had a RAID1 of 2x 500GB SSDs, and one went back to Samsung for RAM which is why it's missing now. 

 

They're sending me a new drive today that will replace the missing RAID1 member, I'm assuming it will be a whole new drive/new serial number.

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5 minutes ago, johnnie.black said:

Yep, my bad:


btrfs device delete missing /mnt/cache

 

Woo, wonderful! Back to showing a 500GB drive now.

 

I also made a full backup before I did this just incase, but I will plan to follow the link from your first post to add a new drive and have it be 2 slots 

 

This will RAID1 the 2 drives and I shouldn't loose any data from what I'm understanding?

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