| SSD Acceleration test | |
|---|---|
 | |
| Participants | |
| Skills | Linux |
| Status | Active |
| Niche | Software |
| Purpose | Infra |
| Tool | No |
| Location | Server room |
| Cost | 0 |
| Tool category | |
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In preparation of building a new storage environment, I wanted to see if SSD acceleration would help improve IOPS and throughput on a classic HDD array.
In preparation for this, I put together the following machine: An ASUS P5S800-VM with:
- 1Gb RAM
- 1x Intel(R) Celeron(R) CPU 2.66GHz
- 1x Hitachi Deskstar IC35L120AVV207 'boot' disk
- IDE
- 19529728 sectors @ 4096 bits/s (9.3 Gb)
- 1x Hitachi HDT721010SLA360 'storage' disk
- SATA
- 1953525168 sectors @ 4096 bits/s (931.5 Gb)
- 1x Kingston SV300S37A120G 'caching' SSD
- SATA
- 234441648 sectors @ 4096 bits/s (111.7 Gb)
Using fio and [1], I have tested the raw MB/s and IOPS for each device, using the default 32Mb file size: (Graphs coming soon)
- Boot:
- randread, 64 users, 8K blocks: 1.7 MB/s , 288 ms latency, 219 IOPS
- randrw, 64 users, 8K blocks: 0.68 MB/s , 385 ms latency, 86 IOPS
- read, 64 users, 8K blocks: 32 MB/s , 15 ms latency, 4207 IOPS
- write, 64 users, 8K blocks: 20 MB/s , 24 ms latency, 2569 IOPS
- Storage:
- randread, 64 users, 8K blocks: 1.7 MB/s , 283 ms latency, 222 IOPS
- randrw, 64 users, 8K blocks: 0.832 MB/s , 305 ms latency, 106 IOPS
- read, 64 users, 8K blocks: 34.2 MB/s , 14.5 ms latency, 4381 IOPS
- write, 64 users, 8K blocks: 17.4 MB/s , 27 ms latency, 2220 IOPS
- Caching:
- randread, 64 users, 8K blocks: 8 MB/s , 0.46 ms latency, 2060 IOPS
- randrw, 64 users, 8K blocks: 10 MB/s , 23.7 ms latency, 1348 IOPS
- read, 64 users, 8K blocks: 29.7 MB/s , 16.2 ms latency, 3811 IOPS
- write, 64 users, 8K blocks: 20.9 MB/s , 23.6 ms latency, 2683 IOPS
We can see the SSD provides about the same QOS for linear rw operations, but is significantly better at random rw than the spinning disks. This is not unexpected.
A write-back dmsetup cache system was constructed using the following configuration:
root@roger-wilco:~# dmsetup ls roger--wilco--vg-swap (254:2) roger--wilco--vg-root (254:0) ssd-metadata (254:3) ssd-blocks (254:4) cached-disk (254:6) vg0-spindle (254:5) root@roger-wilco:~# dmsetup table ssd-metadata 0 924000 linear 8:33 0 root@roger-wilco:~# dmsetup table ssd-blocks 0 233515600 linear 8:33 924000 root@roger-wilco:~# dmsetup table cached-disk 0 1953513472 cache 254:3 254:4 254:5 512 1 writeback default 0 root@roger-wilco:~# vgs VG #PV #LV #SN Attr VSize VFree roger-wilco-vg 1 3 0 wz--n- 114.80g 0 vg0 1 1 0 wz--n- 931.51g 0 root@roger-wilco:~# pvs PV VG Fmt Attr PSize PFree /dev/sda5 roger-wilco-vg lvm2 a-- 114.80g 0 /dev/sdb1 vg0 lvm2 a-- 931.51g 0 root@roger-wilco:~# lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert home roger-wilco-vg -wi-ao---- 103.49g root roger-wilco-vg -wi-ao---- 9.31g swap roger-wilco-vg -wi-ao---- 2.00g spindle vg0 -wi-ao---- 931.51g
- Cached:
- randread, 64 users, 8K blocks: 26.7 MB/s , 18.5 ms latency, 3423 IOPS
- randrw, 64 users, 8K blocks: 5.36 MB/s , 46.6 ms latency, 686 IOPS
- read, 64 users, 8K blocks: 30.1 MB/s , 16.5 ms latency, 3857 IOPS
- write, 64 users, 8K blocks: 1 MB/s , 477 ms latency, 127 IOPS
With this setup, we see a tradeoff between linear write and random write. Linear write is significantly slowed for some reason - some issue with the writeback configuration?