Hi
During rados bench tests, I noticed that HDD usage goes to 100% but SSD stays at ( or very close to 0)
Since I created OSD with BLOCK/WAL on SSD, shouldnt I see some "activity' on SSD ?
How can I be sure CEPH is actually using SSD for WAL /DB ?
Note
I only have 2 HDD and one SSD per server for now
Comands used
rados bench -p rbd 50 write -t 32 --no-cleanup && rados bench -p rbd -t 32 50 rand
/usr/sbin/ceph-volume --cluster ceph lvm create --bluestore --data /dev/sdc --block.wal /dev/disk/by-partuuid/32ffde6f-7249-40b9-9bc5-2b70f0c3f7ad --block.db /dev/disk/by-partuuid/2d9ab913-7553-46fc-8f96-5ffee028098a
( partitions are on SSD ...see below)
sgdisk -p /dev/sda
Disk /dev/sda: 780140544 sectors, 372.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 5FE0EA74-7E65-45B8-A356-62240333491E
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 780140510
Partitions will be aligned on 2048-sector boundaries
Total free space is 520093629 sectors (248.0 GiB)
Number Start (sector) End (sector) Size Code Name
1 251660288 253757439 1024.0 MiB FFFF ceph WAL
2 2048 62916607 30.0 GiB FFFF ceph DB
3 253757440 255854591 1024.0 MiB FFFF ceph WAL
4 62916608 125831167 30.0 GiB FFFF ceph DB
5 255854592 257951743 1024.0 MiB FFFF ceph WAL
6 125831168 188745727 30.0 GiB FFFF ceph DB
7 257951744 260048895 1024.0 MiB FFFF ceph WAL
8 188745728 251660287 30.0 GiB FFFF ceph DB
[root@osd04 ~]# ls -al /dev/disk/by-partuuid/
total 0
drwxr-xr-x 2 root root 200 Apr 26 15:39 .
drwxr-xr-x 8 root root 160 Apr 27 08:45 ..
lrwxrwxrwx 1 root root 10 Apr 27 09:38 0baf986d-f786-4c1a-8962-834743b33e3a -> ../../sda8
lrwxrwxrwx 1 root root 10 Apr 27 09:38 2d9ab913-7553-46fc-8f96-5ffee028098a -> ../../sda2
lrwxrwxrwx 1 root root 10 Apr 27 09:38 32ffde6f-7249-40b9-9bc5-2b70f0c3f7ad -> ../../sda3
lrwxrwxrwx 1 root root 10 Apr 27 09:38 3f4e2d47-d553-4809-9d4e-06ba37b4c384 -> ../../sda6
lrwxrwxrwx 1 root root 10 Apr 27 09:38 3fc98512-a92e-4e3b-9de7-556b8e206786 -> ../../sda1
lrwxrwxrwx 1 root root 10 Apr 27 09:38 64b8ae66-cf37-4676-bf9f-9c4894788a7f -> ../../sda7
lrwxrwxrwx 1 root root 10 Apr 27 09:38 96254af9-7fe4-4ce0-886e-2e25356eff81 -> ../../sda5
lrwxrwxrwx 1 root root 10 Apr 27 09:38 ae616b82-35ab-4f7f-9e6f-3c65326d76a8 -> ../../sda4
dm-0 | busy 90% | | read 2516 | write 0 | | KiB/r 512 | KiB/w 0 | | MBr/s 125.8 | MBw/s 0.0 | | avq 10.65 | avio 3.57 ms | |
LVM | dm-1 | busy 80% | | read 2406 | write 0 | | KiB/r 512 | KiB/w 0 | | MBr/s 120.3 | MBw/s 0.0 | | avq 12.59 | avio 3.30 ms | |
DSK | sdc | busy 90% | | read 5044 | write 0 | | KiB/r 256 | KiB/w 0 | | MBr/s 126.1 | MBw/s 0.0 | | avq 19.53 | avio 1.78 ms | |
DSK | sdd | busy 80% | | read 4805 | write 0 | | KiB/r 256 | KiB/w 0 | | MBr/s 120.1 | MBw/s 0.0 | | avq 23.97 | avio 1.65 ms | |
DSK | sda | busy 0% | | read 0 | write 7 | | KiB/r 0 | KiB/w 10 | | MBr/s 0.0 | MBw/s 0.0 | | avq 0.00 | avio 0.00 ms | |
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