bad PEBs, new router, is this a problem?

[shaft]

I purchased a RT-AX88U Pro from Amazon and it reported 3 bad PEBs out of the box. I searched online and found that most people start at 0 bad PEBs, so I ordered a second RT-AX88U Pro and frustratingly it reports 1 bad PEB out of the box. Is this a problem?

My last router, a RT-AX88U suffered an untimely death at 4.5 years old so I worry about longevity. I know I am probably making mountains out of mole hills, but I really wanted to have all of my erase blocks working.

 

[Justinh]

What is a "PEB" and how do you know how many bad ones you have?

 

[shaft]

It is noted in my router log.

A PEB is a physical erase block. My first new router reported 3 bad PEBs brand new out of the box, and reported that it had 37 PEBs remaining for bad PEB handling. It is my understanding that once these flash cells are used up, the partitions on the router are mounted read only and the router dies.

My current router reports 1 bad PEB and 39 remaining.

 

[shaft]

Generally speaking, PEB (physical erase block) is fixed-sized container that includes a number of logical blocks (physical sectors or NAND flash pages). PEB has a block bitmap with the goal of tracking the state (free, pre-allocated, allocated, invalid) of logical blocks. PEBs contains LEBs or logical erase blocks. LEBs are typically slightly smaller than the PEB that the NAND flash has. For example if the NAND has 128KiB PEB, then the LEB size would be around 126KiB.

 

[RMerlin]

Bad blocks is not uncommon in NAND. These are typically mapped and replaced by spare blocks. Having a few of them is not an issue. it's just that the kernel driver is very open about it, rather than hiding it behind the scene.

 

[shaft]

Then I suppose my question is, how many bad blocks should be tolerated for a new device? Where is the threshold of a device that should be returned? This is akin to bad monitor pixels, I have read about people returning them for as few as one bad pixel. I have read quite a few posted router logs and seen 0 bad PEBs in most of them, or the others have high numbers and huge issues. These bad blocks out of the gate could negatively affect the routers usable life, that is why I am concerned. I also tend to reinitialize or re-flash my router more frequently than the average consumer, as I suspect others on this forum do as well.

I am probably just being pedantic...

 

[RMerlin]

If bad blocks are reported in the system log, it means they were already mapped at the factory, and therefore they are considered normal and fit for selling.

I never paid attention to it, but I remember at least one of my numerous routers had 3 bad blocks (two on one rootfs, and one on the second rootfs.

 

[Volt]

My recently purchased RT-AX82U V2 came with two corrupted PEBs right out of the box. However, judging by what is written in the UBI documentation, this is normal for NAND, and the initial number of corrupted PEBs does not in any way affect the expected reliability of a particular memory chip. Just watch that their number does not increase quickly, otherwise this may indicate a defective memory. For example, in my case, their number has not increased six months later.