List more than 32 uberblocks

[dopeelf]

Is there a way to list more than the last 32 uberblocks? Accidentally deleted some data. The closest txg i can find is about 100 higher than the txg I need.

 

[dopeelf]

I guess I am asking the wrong question or that my endeavors are futile.

 

[Arwen]

There are a limited number of Uberblocks, so it's possible your 32 limit is actual number on your pool.

Further, if I remember correctly, one of the odd things using 4096 byte sector, is a reduction in Uberblocks.

 

[dopeelf]

There are a limited number of Uberblocks, so it's possible your 32 limit is actual number on your pool.

Further, if I remember correctly, one of the odd things using 4096 byte sector, is a reduction in Uberblocks.

Thanks for the reply! I stumbled upon something in in the same lines yesterday. If I remember correctly there is 128K that is used for the uberblocks and if the vdev is created with ashift = 12 (4096) there is only room for 32 uberblocks.

I am pretty sure I am at the end of this journey. It's kind of a perfect storm really since it's the first time I am doing major upgrades to my offsite backup server at the same time as my main server. I guess the lesson I learned is to be really careful if you are "re-deploying" all servers at the same time or just not do all of them at the same time.

 

[Arwen]

Your explanation makes sense.

Sorry it came down to this.

I don't know if a change in ZFS should be made because of the reduction. Meaning, when using 4096 byte sectors, use 1Megabyte for the Uberblocks. That would come out to 256 Uberblocks for either 512 or 4096. Or maybe even allow at pool creation setting a specific amount of Uberblocks, with perhaps 32 as the minimum.

I'd consider putting in a request for enhancement to OpenZFS.