我有一个ProLiant DL380 Gen9服务器HP 智能阵列 P440ar控制器和HP MO0400JEFPA 400GB SASSSD 驱动器。
该服务器用于托管写入密集型数据库，因此我对写入速度特别感兴趣。
我们有 4 个阵列：3 个 raid-1 阵列，每个阵列有 2 个驱动器，还有一个 raid-10 阵列，有 16 个驱动器，用于存储数据。
我一直在使用 dd 测量写入速度：
time sh -c "dd if=/dev/zero of=test.tmp bs=8k count=200000000 conv=fdatasync"
在 raid-1 阵列上，我获得的速度约为 600MB/s（接近该驱动器的理论 700MBPS）。但在 raid-10 阵列上，我仅获得 1.5GB/s。据我了解，使用 16 个驱动器的 raid-10 阵列，理论上我应该获得 8 倍的写入速度。而我仅获得了 3 倍。我应该对此有更高的期望吗？或者实际性能与理论值相差这么远？（在读取速度上，我也获得了 3 倍，而不是理论的 16 倍）。
这是我从 hpssacli 获取的数组的配置：
Smart Array P440ar in Slot 0 (Embedded)
Bus Interface: PCI
Slot: 0
Serial Number: xxxxxxxxxxxx
Cache Serial Number: xxxxxxxxxxxx
RAID 6 (ADG) Status: Enabled
Controller Status: OK
Hardware Revision: B
Firmware Version: 4.52
Rebuild Priority: High
Expand Priority: Medium
Surface Scan Delay: 3 secs
Surface Scan Mode: Idle
Parallel Surface Scan Supported: Yes
Current Parallel Surface Scan Count: 1
Max Parallel Surface Scan Count: 16
Queue Depth: Automatic
Monitor and Performance Delay: 60 min
Elevator Sort: Enabled
Degraded Performance Optimization: Disabled
Inconsistency Repair Policy: Disabled
Wait for Cache Room: Disabled
Surface Analysis Inconsistency Notification: Disabled
Post Prompt Timeout: 15 secs
Cache Board Present: True
Cache Status: OK
Cache Ratio: 0% Read / 100% Write
Drive Write Cache: Enabled
Total Cache Size: 2.0 GB
Total Cache Memory Available: 1.8 GB
No-Battery Write Cache: Disabled
SSD Caching RAID5 WriteBack Enabled: True
SSD Caching Version: 2
Cache Backup Power Source: Batteries
Battery/Capacitor Count: 1
Battery/Capacitor Status: OK
SATA NCQ Supported: True
Spare Activation Mode: Activate on physical drive failure (default)
Controller Temperature (C): 55
Cache Module Temperature (C): 45
Number of Ports: 2 Internal only
Encryption: Disabled
Express Local Encryption: False
Driver Name: hpsa
Driver Version: 3.4.14
Driver Supports HPE SSD Smart Path: True
PCI Address (Domain:Bus:Device.Function): 0000:03:00.0
Negotiated PCIe Data Rate: PCIe 3.0 x8 (7880 MB/s)
Controller Mode: RAID
Controller Mode Reboot: Not Required
Latency Scheduler Setting: Disabled
Current Power Mode: MaxPerformance
Host Serial Number: xxxxxxxxxxx
Sanitize Erase Supported: True
Primary Boot Volume: None
Secondary Boot Volume: None
对于 raid-10 阵列，我得到：
Array: D
Interface Type: Solid State SAS
Unused Space: 0 MB (0.0%)
Used Space: 5.8 TB (100.0%)
Status: OK
MultiDomain Status: OK
Array Type: Data Spare Type: dedicated
HPE SSD Smart Path: disable
Logical Drive: 4
Size: 2.9 TB
Fault Tolerance: 1+0
Heads: 255
Sectors Per Track: 32
Cylinders: 65535
Strip Size: 256 KB
Full Stripe Size: 2048 KB
Status: OK
MultiDomain Status: OK
Caching: Disabled
Unique Identifier: xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Disk Name: /dev/sdd
Mount Points: /data 2.9 TB Partition Number 2
OS Status: LOCKED
Logical Drive Label: xxxxxxxxxxxxxxxxxxxxxxxxxxx
Mirror Group 1:
physicaldrive 1I:1:7 (port 1I:box 1:bay 7, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:8 (port 1I:box 1:bay 8, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:9 (port 1I:box 1:bay 9, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:10 (port 1I:box 1:bay 10, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:11 (port 1I:box 1:bay 11, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:12 (port 1I:box 1:bay 12, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:13 (port 1I:box 1:bay 13, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:14 (port 1I:box 1:bay 14, Solid State SAS, 400 GB, OK)
Mirror Group 2:
physicaldrive 1I:1:15 (port 1I:box 1:bay 15, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:16 (port 1I:box 1:bay 16, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:17 (port 1I:box 1:bay 17, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:18 (port 1I:box 1:bay 18, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:19 (port 1I:box 1:bay 19, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:20 (port 1I:box 1:bay 20, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:21 (port 1I:box 1:bay 21, Solid State SAS, 400 GB, OK)
physicaldrive 1I:1:22 (port 1I:box 1:bay 22, Solid State SAS, 400 GB, OK)
Drive Type: Data
LD Acceleration Method: All disabled
physicaldrive 1I:1:7
Port: 1I
Box: 1
Bay: 7
Status: OK
Drive Type: Data Drive
Interface Type: Solid State SAS
Size: 400 GB
Drive exposed to OS: False
Native Block Size: 4096
Firmware Revision: HPD2
Serial Number: xxxxxxxxxx
Model: HP MO0400JEFPA
Current Temperature (C): 26
Maximum Temperature (C): 36
Usage remaining: 99.74%
Power On Hours: 6982
Estimated Life Remaining based on workload to date: 111600 days
SSD Smart Trip Wearout: False
PHY Count: 2
PHY Transfer Rate: 12.0Gbps, Unknown
Drive Authentication Status: OK
Carrier Application Version: 11
Carrier Bootloader Version: 6
Sanitize Erase Supported: False
（所有驱动器的配置方式完全相同）。
RAID 控制器有问题吗？配置有误吗？3 倍写入速度能让我满意吗？还是我应该在其他地方寻找瓶颈？
答案1
对于 SSD raid 性能，youtube 上的“Linus Tech Tips”频道制作了一个视频显示 raid-0 中 ssd 的性能，不确定它是否也适合您，但绝对值得一试。
视频的结论显示，每增加一个 SSD，性能就会提高 50%。例如
- 1 SSD 具有默认速度。
- 2 SSD 总共将速度提高了 50%。
- 3 SSD 总共将速度提高了 25%。
- 4 SSD 总共将速度提高了 12.5%。
如果您想要真正高性能，最好使用 PCIe-SSD 或 M.2 SSD。
M.2 SSD 的起始读取速度为 3200MB/s，写入速度为 1500MB/s（三星 960 EVO 250GB）。但我的意思是，真正好的性能会花费很多钱。
答案2
我会尝试改变这些：
Cache Ratio: 0% Read / 100% Write
SSD Caching RAID5 WriteBack Enabled: True