lightrush

cross-posted from: https://lemmy.ca/post/31824976

Lately I've had some obviously inaccurate measurements from my Timemore Black Mirror scale. That would happen occasionally but not always. I was charging it today and as luck would have it, I was sitting beside it. I typically charge it unattended. I noticed that it took a very long time to charge and multiple times it seemed to restart charging. I grabbed it to check the cable and noticed it was quite warm in one spot. I though - that's alright, it's likely where the battery cell is, it's charging, lithium cells get warm during charging. Later I took it off the charger and while handling it I examined the hot spot a bit more. I noticed that when I squeezed the scale at that corner, the top plate wouldn't sink towards the bottom as it does in the other corners. A few mental calculations later I figured this could be a swollen cell that has grown so large that it impacts the plates and doesn't let them come together as they do normally. I took it apart. Lo and behold this spicy pillow:

The marking on it means it's supposed to be 8mm thick. It's currently closer to 12.5mm. Removing the battery allowed the two plates to come together in all corners as normal. That confirmed the hypothesis. Further, the reason why it only occasionally impacted the measurements is likely due to the weight of the cup I was using. When using a lighter cup, the total weight would be lower than needed to get the two plate to touch the battery and produce inaccurate measurement.

I ordered this as a replacement. It fits the dimensions and it's got some safety certification.

To check if your scale is a fire hazard, squeeze this corner:

Normal squeeze action looks like this. Unfortunately I didn't record a video prior to removing the battery.

If it the two plates come together as the do in the other corners, you're probably okay. If the plates don't come nearly as close, you've got an unlit petard in your hands.

Lately I've had some obviously inaccurate measurements from my Timemore Black Mirror scale. That would happen occasionally but not always. I was charging it today and as luck would have it, I was sitting beside it. I typically charge it unattended. I noticed that it took a very long time to charge and multiple times it seemed to restart charging. I grabbed it to check the cable and noticed it was quite warm in one spot. I though - that's alright, it's likely where the battery cell is, it's charging, lithium cells get warm during charging. Later I took it off the charger and while handling it I examined the hot spot a bit more. I noticed that when I squeezed the scale at that corner, the top plate wouldn't sink towards the bottom as it does in the other corners. A few mental calculations later I figured this could be a swollen cell that has grown so large that it impacts the plates and doesn't let them come together as they do normally. I took it apart. Lo and behold this spicy pillow:

The marking on it means it's supposed to be 8mm thick. It's currently closer to 12.5mm. Removing the battery allowed the two plates to come together in all corners as normal. That confirmed the hypothesis. Further, the reason why it only occasionally impacted the measurements is likely due to the weight of the cup I was using. When using a lighter cup, the total weight would be lower than needed to get the two plate to touch the battery and produce inaccurate measurement.

I ordered this as a replacement. It fits the dimensions and it's got some safety certification.

To check if your scale is a fire hazard, squeeze this corner:

Normal squeeze action looks like this. Unfortunately I didn't record a video prior to removing the battery.

If it the two plates come together as the do in the other corners, you're probably okay. If the plates don't come nearly as close, you've got an unlit petard in your hands.

cross-posted from: https://lemmy.ca/post/30850573

cross-posted from: https://lemmy.ca/post/30593626

#donglelife

Apparently this isn't allowed in !Android and should go here instead.

A Chromecast with Google TV connected to a USB-C hub, connected to an Ethernet dongle, connected to an HDMI coupler.

I'm syncoiding from my normal RAIDz2 to a backup mirror made of 2 disks. I looked at zpool iostat and I noticed that one of the disks consistently shows less than half the write IOPS of the other:

                                        capacity     operations     bandwidth 
pool                                  alloc   free   read  write   read  write
------------------------------------  -----  -----  -----  -----  -----  -----
storage-volume-backup                 5.03T  11.3T      0    867      0   330M
  mirror-0                            5.03T  11.3T      0    867      0   330M
    wwn-0x5000c500e8736faf                -      -      0    212      0   164M
    wwn-0x5000c500e8737337                -      -      0    654      0   165M

This is also evident in iostat:

     f/s f_await  aqu-sz  %util Device
    0.00    0.00    3.48  46.2% sda
    0.00    0.00    8.10  99.7% sdb

The difference is also evident in the temperatures of the disks. The busier disk is 4 degrees warmer than the other. The disks are identical on paper and bought at the same time.

Is this behaviour expected?

I built a 5x 16TB RAIDz2, filled it with data, then I discovered the following.

Sequentially reading a single file from the file system gave me around 40MB/s. Reading multiple in parallel brought the total throughput in the hundreds of megabytes - where I'd expect it. This is really weird. The 5 disks show 100% utilization during single file reads. Writes are supremely fast, whether single threaded or parallel. Reading directly from each disk gives >200MB/s.

Splitting the the RAIDz2 into two RAIDz1s, or into one RAIDz1 and a mirror improved reads to 100 and something MB/s. Better but still not where it should be.

I have an existing RAIDz1 made of 4x 8TB disks on the same machine. That one reads with 250-350MB/s. I made an equivalent 4x 16TB RAIDz1 from the new drives and that read with about 100MB/s. Much slower.

All of this was done with ashift=12 and default recordsize. The disks' datasheets say their block size is 4096.

I decided to try RAIDz2 with ashift=13 even though the disks really say they've got 4K physical block size. Lo and behold, the single file reads went to over 150MB/s. 🤔

Following from there, I got full throughput when I increased the recordsize to 1M. This produces full throughput even with ashift=12. My existing 4x 8TB RAIDz1 pools with ashift=12 and recordsize=128K read single files fast.

Here's a diff of the queue dump of the old and new drives. The left side is a WD 8TB from the existing RAIDz1, the right side is one of the new HC550 16TB

< max_hw_sectors_kb: 1024
***
> max_hw_sectors_kb: 512
20c20
< max_sectors_kb: 1024
***
> max_sectors_kb: 512
25c25
< nr_requests: 2
***
> nr_requests: 60
36c36
< write_cache: write through
***
> write_cache: write back
38c38
< write_zeroes_max_bytes: 0
***
> write_zeroes_max_bytes: 33550336

Could the max_*_sectors_kb being half on the new drives have something to do with it?

Can anyone make any sense of any of this?

I wasn't aware Steve Paikin and John McGrath had a podcast on Ontario politics. I like it!