Trim on gmirrored SSDs is slow and results in inresponsive system

[Robert Schulze]

Hi,

Am 04.03.2015 um 17:09 schrieb Steven Hartland:
> Transaction sizes look like they are the same but the tps from gmirror
> is significantly lower.
> 
> As iostat doesn't properly understand deletes it would still be nice to
> see that gstat -d -p output as that will also give us queue depth.

Since gstat doesnt just output row by row, I had to screenshot a running
gstat and transcribe the values. Running gstat -b in a loop doesn't help
here, since the system is inresponsive and won't start any program in
time during the DELETE ops.

So after deleting a 2GB file on a gmirror with two active SSDs I get:

# gstat -dpfada -I3s

dT: 3.189s  w: 3.000s  filter: ada
L(q) ops/s r/s kBps ms/r w/s kBps ms/w  d/s   kBps ms/d %busy Name
0     3342   0    0  0.0   0    0  0.0 3342 106939 10.2  80.5| ada0
0     3342   0    0  0.0   0    0  0.0 3342 106939 10.0  82.0| ada1

9     2606   0    0  0.0   0    0  0.0 2606  83400 60.8  98.3| ada0
9     2606   0    0  0.0   0    0  0.0 2606  83400 56.9  98.7| ada1

46    1705   0    0  0.0   0    0  0.0 1705  54565 62.5  98.4| ada0
51    1704   0    0  0.0   0    0  0.0 1704  54512 62.9  97.6| ada1

22    1540   0    0  0.0   0    0  0.0 1540  49285 20.9  96.6| ada0
24    1541   0    0  0.0   0    0  0.0 1541  49317 21.8  96.0| ada1

2     1496   0    0  0.0   0    0  0.0 1496  47887 13.3  98.6| ada0
7     1495   0    0  0.0   0    0  0.0 1495  47855 14.1  98.9| ada1

11    1032   0    0  0.0   0    0  0.0 1032  33010 18.2  98.8| ada0
10    1033   0    0  0.0   0    0  0.0 1033  33070 15.4  98.1| ada1

12     775   0    0  0.0   0    0  0.0  775  24798 26.2  97.5| ada0
16     773   0    0  0.0   0    0  0.0  773  24746 29.6  98.5| ada1

65     743   0    0  0.0   0    0  0.0  743  23784 25.4  98.8| ada0
59     746   0    0  0.0   0    0  0.0  746  23887 24.4  99.0| ada1

> 
> Try backing out r268816 and see if that has any impact.

could you please explain what you mean by that?

regards,
Robert Schulze