hdparm can give you an general idea how a drive performs. You may notice that there's quite the difference between the three outputs above. Timing O_DIRECT disk reads: 1470 MB in 3.00 seconds = 489.76 MB/sec Timing O_DIRECT cached reads: 984 MB in 2.00 seconds = 491.87 MB/sec Timing O_DIRECT disk reads: 464 MB in 3.01 seconds = 154.26 MB/sec Timing O_DIRECT cached reads: 946 MB in 2.00 seconds = 472.43 MB/sec # Western Digital Red (WDC WD30EFRX-68EUZN0) Timing O_DIRECT disk reads: 184 MB in 3.02 seconds = 61.02 MB/sec Timing O_DIRECT cached reads: 122 MB in 2.02 seconds = 60.31 MB/sec
-direct means we by-pass the kernels cache and use O_DIRECT to the drives cache.The typical way of using it is hdparm -direct -t -T /dev/sdX where Hdparm can give an indication of a drives sequential read and reads from a drives and it's cache. However, they will provide you with some very basic data which can help troubleshoot if a drive is connected to a lower SATA version than expected (you should be checking that with smartctl -all /dev/sda but.) and you can get a very rough idea how a drive performs. These methods are highly recommended on a lot of pages on the Internet even though they are close to utterly useless. 3.3 Benchmarking Cloud/VPS storage solutions.3.1 "Shingled magnetic recording" (SMR) drives.2.1.2 Testing sequential write speed with very big blocks.
2.1.1 Testing sequential read speed with very big blocks.2 Methods of testing I/O performance which gives useful information reflecting real-world use.
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