[Bug 211713] NVME controller failure: resetting (Samsung SM961 SSD Drives)

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=211713

--- Comment #37 from stb at lassitu.de ---
[root at foo ~]# diskinfo -t /dev/nvd0
/dev/nvd0
        512             # sectorsize
        128035676160    # mediasize in bytes (119G)
        250069680       # mediasize in sectors
        0               # stripesize
        0               # stripeoffset
        S347NY0HB01730  # Disk ident.

Seek times:
        Full stroke:      250 iter in   0.014551 sec =    0.058 msec
        Half stroke:      250 iter in   0.015022 sec =    0.060 msec
        Quarter stroke:   500 iter in   0.029067 sec =    0.058 msec
        Short forward:    400 iter in   0.015134 sec =    0.038 msec
        Short backward:   400 iter in   0.015675 sec =    0.039 msec
        Seq outer:       2048 iter in   0.063374 sec =    0.031 msec
        Seq inner:       2048 iter in   0.057973 sec =    0.028 msec

Transfer rates:
        outside:       102400 kbytes in   0.094174 sec =  1087349 kbytes/sec
        middle:        102400 kbytes in   0.089065 sec =  1149722 kbytes/sec
        inside:        102400 kbytes in   0.089141 sec =  1148742 kbytes/sec

I think I should be getting 2.2GB/s. With 4 concurrent dd's, gstat shows:

[root at foo ~]# gstat -I60s -f '^....$'
dT: 60.002s  w: 60.000s  filter: ^....$
 L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
    4  13578  13578 1737975    0.3      0      0    0.0  100.0| nvd0

[root at foo ~]# for i in 0 1 2 3; do dd if=/dev/nvd0 of=/dev/null bs=1m
count=100k & done; wait; echo 'done'
[1] 41520
[2] 44578
[3] 46696
[4] 47833
102400+0 records in
102400+0 records out
107374182400 bytes transferred in 192.262522 secs (558476927 bytes/sec)
[1]   Done                    dd if=/dev/nvd0 of=/dev/null bs=1m count=100k
102400+0 records in
102400+0 records out
107374182400 bytes transferred in 241.421031 secs (444759026 bytes/sec)
[2]   Done                    dd if=/dev/nvd0 of=/dev/null bs=1m count=100k
102400+0 records in
102400+0 records out
107374182400 bytes transferred in 241.552144 secs (444517613 bytes/sec)
[3]-  Done                    dd if=/dev/nvd0 of=/dev/null bs=1m count=100k
102400+0 records in
102400+0 records out
107374182400 bytes transferred in 241.559861 secs (444503412 bytes/sec)
[4]+  Done                    dd if=/dev/nvd0 of=/dev/null bs=1m count=100k
done

So I'm guessing the penalty is not too big.  The 128 GB model has a
significantly lower write speed compared to the 256GB and 512GB models (around
800MB/s I believe), so I didn't test that.

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