前言

在前一篇接 USB複製 ISO檔看到的速度有疑惑，來找一些磁碟效能測試工具實測看看。

過去已有認知，有不同情境下的效能指標：

• 讀/寫
• 小檔/大檔
• 連續/隨機
  檔案系統、架構設計也會有影響。

先把範圍定在試試幾個 Linux 下的磁碟效能測試工具，
簡略測測看這台小主機的 SSD、USB 讀寫效能。
看看手上消費級產品的效能。

Proxmox 就這樣先被當 Linux主機玩

hdparm

起手先安裝

apt-get install hdparm

先看 hdparm -h 注意到測讀取為主，其它功能見 manpage

• https://manpages.debian.org/bookworm/manpages-zh/hdparm.8.zh_TW.html
• 常見用來測試的參數
• -t Perform device read timings
• -T Perform cache read timings
• --direct
  Use the kernel´s "O_DIRECT" flag when performing a -t timing test. This bypasses the page cache, causing
  the reads to go directly from the drive into hdparm's buffers, using so-called "raw" I/O. In many cases,
  this can produce results that appear much faster than the usual page cache method, giving a better indica‐
  tion of raw device and driver performance.

不用掛載磁碟，接上後即可測 (可在 dmesg -T 看到是否有偵測到)

• M2 SSD

~# hdparm -tT /dev/nvme0n1

/dev/nvme0n1:
 Timing cached reads:   19640 MB in  2.00 seconds = 9832.56 MB/sec
 Timing buffered disk reads: 4312 MB in  3.00 seconds = 1437.17 MB/sec
 

~# hdparm -tT --direct /dev/nvme0n1

/dev/nvme0n1:

 Timing O_DIRECT cached reads:   2858 MB in  2.00 seconds = 1429.07 MB/sec
 Timing O_DIRECT disk reads: 4474 MB in  3.00 seconds = 1490.89 MB/sec

• SATA 介面的 2.5" SSD

~# hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   19250 MB in  2.00 seconds = 9637.01 MB/sec
 Timing buffered disk reads: 1590 MB in  3.00 seconds = 529.71 MB/sec
 
~# hdparm -tT --direct /dev/sda

/dev/sda:
 Timing O_DIRECT cached reads:   962 MB in  2.00 seconds = 480.85 MB/sec
 Timing O_DIRECT disk reads: 1458 MB in  3.00 seconds = 485.55 MB/sec

• USB隨身碟(G牌)，接在 USB3.0 接口

~# hdparm -tT  /dev/sdb

/dev/sdb:
 Timing cached reads:   19438 MB in  2.00 seconds = 9732.02 MB/sec
 Timing buffered disk reads: 310 MB in  3.02 seconds = 102.68 MB/sec


~# hdparm -tT --direct /dev/sdb

/dev/sdb:
 Timing O_DIRECT cached reads:   204 MB in  2.02 seconds = 101.05 MB/sec
 Timing O_DIRECT disk reads: 304 MB in  3.02 seconds = 100.79 MB/sec

• USB隨身碟(G牌)，接在 USB2.0 接口

~# hdparm -tT /dev/sdb

/dev/sdb:
 Timing cached reads:   18248 MB in  2.00 seconds = 9134.54 MB/sec
 Timing buffered disk reads: 126 MB in  3.01 seconds =  41.93 MB/sec


~# hdparm -tT --direct /dev/sdb

/dev/sdb:
 Timing O_DIRECT cached reads:    80 MB in  2.04 seconds =  39.17 MB/sec
 Timing O_DIRECT disk reads: 120 MB in  3.00 seconds =  39.99 MB/sec

• 注意到沒使用 --direct 時， Timing cached reads 數字都漂亮到誇張…

有個有點妙的 -H ，

• -H Read temperature from drive (Hitachi only)
  剛好手上有顆外接的 2.5吋硬碟，真的只對這家有效

~ $ hdparm -H /dev/sdb

/dev/sdb:
 drive temperature (celsius) is:  35
 drive temperature in range:  yes

不同家的讀不到正常數據

~ $ hdparm -H /dev/sda

/dev/sda:
SG_IO: bad/missing sense data, sb[]:  70 00 0b 00 00 00 00 0a 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 drive temperature (celsius) is:  under -20
 drive temperature in range:  yes

• 看硬碟資訊的

• -i Display drive identification

• -I Detailed/current information directly from drive

• • 另外查看硬碟訊息個人常用 smartctl

• M2 SSD 另外要裝 nvme-cli 。 nvme smart-log /dev/nvme0n1
  歪樓不在效能測試的主題，又有點零散，先這樣。

另外

• 傳統硬碟常見硬碟前後段速度會有差異 (等角速度下，內外圈磁錄密度)。
• SSD 情況略有不同，儲存跟資料讀寫的技術也會影響效能，亦有的設計會在儲存空間低於一定比例後打折。
  近年各式新的儲存技術對效能的影響也是個可以試的題材…

參考資料

• https://www.alexleo.click/io_bench_how_to/

  • 列出了不少參考資料

• https://www.akitio.com.tw/view-article/186-usb-3-0

  • 一家外接儲存產品的 USB3.0外接硬碟 測試 (file size 500MB, sequential)