On Sat, Mar 28, 2020 at 8:26 PM Nir Soffer <[email protected]> wrote:

>
>
> Gluster disks are thin (raw-sparse) by default just like any other
> file based storage.
>
> If this theory was correct, this would fail consistently on gluster:
>
> 1. create raw sparse image
>
>     truncate -s 100g /rhev/data-center/mnt/glusterSD/server:_path/test
>
> 2. Fill image quickly with data
>
>     dd if=/dev/zero bs=1M | tr "\0" "U" | dd
> of=/rhev/data-center/mnt/glusterSD/server:_path/test bs=1M count=12800
> iflag=fullblock oflag=direct conv=notrunc
>
> According to your theory gluster will fail to allocate shards fast
> enough and fail the I/O.
>
> Nir


Coming back here as I got some other occurrences of the same error and I'm
going to try to enable some logging and see where it is the origin.

In the mean time I confirmed what written by Nir above. No error on gluster
side with the command suggested:

[root@ovirt libvirt]# time dd if=/dev/zero bs=1M | tr "\0" "U" | dd
of="/rhev/data-center/mnt/glusterSD/ovirtst.mydomain.storage:_vmstore/test"
bs=1M count=12800 iflag=fullblock oflag=direct conv=notrunc
12800+0 records in
12800+0 records out
13421772800 bytes (13 GB) copied, 37.8056 s, 355 MB/s

real 0m37.812s
user 0m10.582s
sys 0m24.072s
[root@ovirt libvirt]#
[root@ovirt libvirt]# echo $?
0
[root@ovirt libvirt]#

During the copy a "vmstat 3" produced indeed about 350 MiB/s:

[root@ovirt ~]# vmstat 3
procs -----------memory---------- ---swap-- -----io---- -system--
------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id
wa st
 8  0      0 1274344448 329220 5752988    0    0     8   142    0    0  4
 2 95  0  0
12  0      0 1274341504 329220 5753008    0    0  1930 30079 76558 186828
 7  3 90  0  0
 3  0      0 1274340480 329220 5753028    0    0   917 15786 68796 178179
 6  3 91  0  0
 2  0      0 1274336128 329220 5753048    0    0    61 14219 69035 172374
 6  3 90  0  0
17  2      0 1274334976 329220 5753088    0    0  1931 14814 74888 178985
 7  3 89  0  0
 7  0      0 1274317952 329220 5753112    0    0  1556 144318 72745 257632
 7  3 89  0  0
11  1      0 1274315136 329220 5753112    0    0    91 350458 80783 410853
 8  4 87  1  0
12  0      0 1274310272 329220 5753148    0    0   965 378040 83638 419936
 6  4 89  1  0
10  1      0 1274308352 329220 5753188    0    0  1470 379597 82909 429217
 7  4 88  1  0
 7  0      0 1274318592 329220 5753192    0    0   608 368145 85389 417066
 9  5 86  1  0
 9  1      0 1274323584 329220 5753208    0    0   460 370369 81002 426601
 7  5 88  1  0
12  2      0 1274323456 329220 5753232    0    0  2655 369143 79131 415323
 7  4 88  1  0
10  2      0 1274306560 329220 5753252    0    0   625 367324 82076 419014
 8  4 87  1  0
15  0      0 1274276480 329220 5753272    0    0    99 355281 81662 409003
 8  4 87  1  0
12  2      0 1274259072 329220 5753292    0    0   855 358916 82942 416828
 7  4 88  1  0
 5  0      0 1274257024 329220 5753316    0    0  1566 374178 81489 415783
 7  4 88  1  0
 7  2      0 1274259968 329220 5753324    0    0   527 344149 82577 418192
 7  4 88  1  0
 7  0      0 1274254080 329220 5753364    0    0  1596 341075 82839 414259
 6  4 89  1  0
 7  1      0 1274267776 329220 5753404    0    0  1431 97078 73923 242802
 6  3 90  0  0

Tried 4 times without any error and consistent timing of about 36-37 seconds

Go to next tests
Gianluca
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