The first speed shows how fast disk reads are if the data is already buffered. The disk is never accessed, so it is probably pretty meaningless for a web server (since most of the time disk reads will probably not be buffered). The second stat shows real hard drive read performance. In your case, it means that the web server is reading under 1
Jan 03, 2008 hdparm - Wikipedia Test device read performance speed (-t for timing buffered disk reads) of the first hard drive: sudo hdparm -t /dev/sda Enable energy saving spindown after inactivity (24*5=120 seconds): sudo hdparm -S 24 /dev/sda To retain hdparm settings after a software reset, run: sudo hdparm -K 1 /dev/sda Enable read-ahead: sudo hdparm -A 1 /dev/sda How to check hard disk performance - Ask Ubuntu sudo hdparm -Tt /dev/sda /dev/sda: Timing cached reads: 12540 MB in 2.00 seconds = 6277.67 MB/sec Timing buffered disk reads: 234 MB in 3.00 seconds = 77.98 MB/sec sudo hdparm -v /dev/sda will give information as well. dd will give you information on write speed. If the drive doesn't have a file system (and only then), use of=/dev/sda. What is Java BufferedReader? - Definition from WhatIs.com
Mar 02, 2017
Jul 13, 2011 · I was analyzing the Disk read using hdparm utility. This is what i got as a result. Code: # hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads hmmm well i tried using gdisk but my speeds remain the same, also fdisk reports the same thing as before. Here is what i did, i put gdisk in expert mode with X, used the L option to change sector alignment value, and entered 12288 as the value, then i wrote the table to the disk with w Timing buffer-cache reads: 592 MB in 2.00 seconds = 296.00 MB/sec Timing buffered disk reads: 162 MB in 3.01 seconds = 53.82 MB/sec Timing buffer-cache reads: 576 MB in 2.01 seconds = 286.57 MB/sec Timing buffered disk reads: 166 MB in 3.01 seconds = 55.15 MB/sec Timing buffer-cache reads: 580 MB in 2.00 seconds = 290.00 MB/sec Timing buffered
Oct 02, 2009
Test device read performance speed (-t for timing buffered disk reads) of the first hard drive: sudo hdparm -t /dev/sda Enable energy saving spindown after inactivity (24*5=120 seconds): sudo hdparm -S 24 /dev/sda To retain hdparm settings after a software reset, run: sudo hdparm -K 1 /dev/sda Enable read-ahead: sudo hdparm -A 1 /dev/sda Buffered readers are preferable for more demanding tasks, such as file and streamed readers. Buffering the reads allows large volumes to be read from disk and copied to much faster RAM to increase performance over the multiple network communications or disk reads done with each read command otherwise. Mar 10, 2014 · Question: Why does buffered write() sometimes stall? It just writes to kernel buffer and doesn't hit disk. Answer: 1. write() does disk read when needed. To avoid this issue you need to append a file, not overwrite. Or use OS page aligned writes. 2. write() may be blocked for "stable page writes". Nov 25, 2017 · The operating system takes care of synchronizing file writes back to disk, and reads can be pulled directly from memory. The usage note mentions large files vis-à-vis buffered I/O because: 1.The up-front cost is expensive. The performance penalty with buffered I/O is substantially worse for large files. 2.You get little in return. The Buffer Gets Oracle metric is the number of buffer gets for all cursors. A measurement of CPU usage, excessive buffer gets may indicate that this statement needs to be examined more closely. In the next example we will instruct hdparm to read data from the second half of the disk that is if the hard drive size is 100GB. hdparm --offset 50 -t /dev/sda /dev/sda: Timing buffered disk reads (offset 50 GB): 72 MB in 3.05 seconds = 23.61 MB/sec To obtain cached reads run the following linux command: