If there is a certain amount hard drives as well as flash drives (flash drive), there is a need to determine their performance in order to determine for what purposes to use a particular storage device. Checking the read / write speed of hard drives is usually carried out using hdparm.
hdparm- console utility (previously included in the hwtools package) designed to view and adjust the parameters of hard drives with an interface ATA (parallel interface for connecting drives, hard drives and optical drives, to a computer).
Parameters for hard drives are set with an emphasis on reliability, even on not very high-quality equipment, but on most modern motherboards and hard drives can significantly increase performance IDE subsystems without compromising reliability.
Currently, there are no reliable methods for determining the optimal parameters for devices (except for careful trials and observations) and there is no centralized database (in which information about the observations of experienced users would be collected), then the safest thing is to compare some parameters " default"and, based on them, choosing a device with the most optimal parameters. The easiest way to do this is with hdparm especially since it is included in almost all modern distributions linux.
Although the main purpose hdparm tuning and optimization, it can be used as a simple tool for conducting tests, for this it is enough to execute (hdparm requires admin/root permissions to work):
sudo hdpam -t "device name"
For example:
sudo hdpam -t /dev/sda
You can find out the disk name by running:
Fdisk -l
It is desirable to carry out the test in the absence of noticeable disk activity. Option " -t" allows you to display the speed of sequential data reading from the disk, without delays caused by work file system.
The test performed will show the highest data transfer rate for the drive under test. The read/write check takes place at the very beginning of the disk, at its fastest section, so the numbers obtained do not correspond much to the actual speed of the disk. The most realistic result can be obtained by checking the disk at arbitrary points, in random order... You can carry out such a test using the console utility seeker.
seeker- a console utility that checks the speed of reading / writing hard drives randomly, with access to the disk in random order. In this testing method, the disk head moves quickly from one place to another, reading small pieces of data. The process involves mechanical operations and disk access is much slower than the sequential access test.
Arbitrary verification method used in seeker much closer to real work hard drive and the resulting test results look more believable. Therefore using seeker it is very important to test the entire disk (/dev/sda), not a separate section (/dev/sda1, /dev/sda2, /dev/sda3 etc.):
sudo seeker "disk name"
The utility is easy to use, starts without additional options, disk testing is carried out within thirty seconds, and for more complete access to the disk, it is better to run the utility with administrator rights (root). In addition to hard drives, seeker you can conduct a comparative test of existing flash drives (e.g. to use the fastest device as a LiveUSB).
Original: Test read/write speed of usb and ssd drives with dd command on Linux
Author: Silver Moon
Publication date: Jul 12, 2014
Translation: N.Romodanov
Transfer date: October 2014
Device speed
The speed of a device is measured in units of how much data it can read or write per unit of time. The dd command is a simple tool command line, which can be used to read and write arbitrary blocks of data on disk and measure the speed at which the data transfer has occurred.
In this article, we will use the dd command to check the read and write speed of usb and ssd devices.
The data transfer speed depends not only on the disk, but also on the interface through which it is connected. for instance usb port 2.0 has a maximum functional speed limit of 35 MB/s, so even if you plug a high-speed usb 3 flash drive into the usb 2 port, the speed will be limited to a lower value.
The same applies to the SSD device. The SSD device is connected through SATA ports, which have different versions. Sata 2.0 has a maximum theoretical speed limit of 3Gbps, which is about 375MB/s. While SATA 3.0 supports twice the speed.
Test method
Mount the drive and navigate to it from a terminal window. Then use the dd command to first write the file, which consists of fixed-size blocks. Then read the same file using the same block size.
The general syntax of the dd command is as follows
Dd if=path/to/input_file of=/path/to/output_file bs=block_size count=number_of_blocks
When writing to disk, we simply read from /dev/zero, which is the source of an infinite number of bytes. When reading from disk, we read the previously written file and send it to /dev/null, which doesn't really exist. Throughout the process, the dd command monitors and reports the rate at which the transfer occurs.
SSD device
The SSD device we are using is a "Samsung Evo 120GB" SSD drive. This is an entry level ssd device related to budget and also my first SSD drive. It is also one of the highest performing SSDs available on the market.
In this test disk ssd connected to a sata 2.0 port.
Recording speed
Let's record to ssd first
$ dd if=/dev/zero of=./largefile bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 4.82364 s, 223 MB/s
The block size is actually quite large. You can try using a smaller size like 64k or even 4k.
Reading speed
Now, on the contrary, read the same file. But clear the memory cache first to make sure the file is actually being read from disk.
To clear the memory cache, run the following command
$ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
Now read the file
$ dd if=./largefile of=/dev/null bs=4k 165118+0 records in 165118+0 records out 676323328 bytes (676 MB) copied, 3.0114 s, 225 MB/s
USB device
In this test, we will measure the read speed of ordinary usb flash drives. The devices connect to standard usb 2 ports. The first device is a sony 4gb usb stick and the second is a strontium 16gb.
First connect the device and mount it so that it is readable. Then, from the command line, navigate to the mounted directory.
Sony 4GB device - recording
In this test, the dd command is used to write 10,000 pieces of data of 8 KB each into a single file on disk.
# dd if=/dev/zero of=./largefile bs=8k count=10000 10000+0 records in 10000+0 records out 81920000 bytes (82 MB) copied, 11.0626 s, 7.4 MB/s
The write speed is about 7.5 MB/s. This is a low figure.
Sony 4GB device - reading
The same file is read to test the read speed. To clear the memory cache, run the following command
$ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
Now read the file with dd command
# dd if=./largefile of=/dev/null bs=8k 8000+0 records in 8000+0 records out 65536000 bytes (66 MB) copied, 2.65218 s, 24.7 MB/s
The read speed is approximately 25 MB/s, which is more or less standard for cheap usb sticks.
USB 2.0 has a theoretical maximum signaling rate of 480 Mbps or 60 Mbps. But due to various limitations, the maximum throughput is limited to approximately 280 Mbps or 35 Mbps. In addition, the actual speed depends on the quality of the flash drive, as well as other factors.
And since the usb device described above was connected to a USB 2.0 port and a read speed of 24.7 MB / s was achieved, which is not very bad. But the write speed is far behind.
Now let's do the same test with a Strontium 16gb stick. Strontium is another brand that makes very cheap usb sticks, but these sticks are reliable.
Write speed for Strontium 16gb device
# dd if=/dev/zero of=./largefile bs=64k count=1000 1000+0 records in 1000+0 records out 65536000 bytes (66 MB) copied, 8.3834 s, 7.8 MB/sRead speed for Strontium 16gb device
# sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches" # dd if=./largefile of=/dev/null bs=8k 8000+0 records in 8000+0 records out 65536000 bytes (66 MB) copied, 2.90366 s, 22.6 MB/sData reading speed is slower than Sony device.
Now at an accelerated pace is the modernization of disk subsystems in almost any hosting company. Solid state drives have become a significant breakthrough in improving the performance of computer, including server hardware. The fact is that the disk has been a bottleneck for many years, what is called the "weak link" in the performance of any information systems. In other words, all other components are the processor, RAM, system buses, and even the network - everything has long been much faster and more productive than drives. SSD gives a performance boost to any device by about 3-5 times. This means any applications will run several times faster, sometimes even tens of times faster.
So, the hoster offers you two tariff lines - SSD and non_SSD. You, of course, take an SSD. But how to make sure that the hoster really issued an SSD? After all, there is no difference for the site to work - everything will work for you on a hosting with any disk. That is, theoretically, the hoster can announce to you that he has servers on fast solid-state drives. But in fact, to sell power on conventional traditional HDDs. And you probably won't even know about it.
After all, SSDs are much more expensive than regular drives. And hosters have serious capacities, they need to store terabytes of data. Can you imagine how much such systems can cost, given that 1 GB of solid state drive is about 10 times more expensive than 1 GB of a regular disk?
What is SSD-boost or flashcache?
In general, there is a hybrid system. When using a bunch of SSD + HDD. At the same time, all data is stored on traditional large disks. There is special software that configures these drives into a special tricky array, where the SSD acts as a cache for any data that is written or read. In such an array, we have a small SSD, say 120 GB, and then a large HDD, 2 Tb. Such a bundle gives a read / write speed like that of an SSD, but a volume like that of an HDD. That's it. At the same time, the hoster can easily tell you that he has everything on the SSD. Honest hosters call it SSD-boost. This does not negatively affect the operation of the sites.
I've tested disk speeds with dozens of different hosts. You will be surprised, but only 1 out of 5 hosts provides an “honest” SSD.
I capture these things with screenshots.
Tests of fake SSDs from some hosts
Hoster #1
Here we see only 30 Mb / s per entry. This is the normal speed for a regular HDD. But the hoster declares it as an SSD.
Hoster №2
Similar picture. But the reading speed is already a little better. Perhaps this is the case with flashcache, but very overloaded. And most likely just a raid array of conventional HDDs. You can collect them in such a way that the reading performance increases by 1.5-2 times.
Hoster №3
Favorite hoster. Shows generally wild results. Not only is the HDD, it is also overloaded with disk accesses.
Hoster №4
It's actually a fun story here. Did a client audit of the server, there were complaints about the brakes. Let me check the disk.
Here is such a picture. I write to the client this way and that - the hoster blatantly deceives you. The client runs to support - it turns out really. The client was “forgotten” to turn on the SSD when switching from one tariff to another, you understand? Switch, test again and see how a real SSD appeared.
Real SSD tests
Now, in order to understand the difference, I will show you the screenshots of the tests of a really SSD.
This is how it looks. Recording speed over 100 Mb/s should be. This is the minimum for an SSD. This is a test from my work laptop on which I am currently writing this post. It has the cheapest 120 Gb SSD. As you can see, its speed is 4-5 times faster than that of a traditional disk.
And here is a hoster test that provides a real SSD.
This is definitely a real SSD. This is how it should be. Perhaps a boost is configured, but it's still an SSD and you can live with this hoster.
How to do a disk speed test with a host?
I use dd for this. It is in any linux. But it should be handled with care, otherwise there is a risk of spoiling the entire server in general, all the data on it. Because this utility writes raw data to any device or file you specify.
So, for the write test, you should take a stream of zeros from the special device /dev/zero and send it to a file on the drive under test. Any arbitrary file. For example, in the temporary files folder /tmp/test.img
Dd if=/dev/zero of=/tmp/test.img bs=1M count=1024 oflag=dsync
This command will create a 1 GB file and display the write speed.
You can immediately check the reading speed, only here the if option should point to the created file, and of somewhere into the void. In Linux, there is such a device /dev/null , we will direct it to it:
Dd if=/tmp/test.img of=/dev/null bs=1M count=1024
But before that, you need to reset the disk cache, otherwise the file will be read in a second, and you will see the read speed in Gb / s. This is done with the following command:
Sysctl vm.drop_caches=3
After that, we conduct a reading test with the second team.
Well, at the end, you need to delete the test file so that it does not take up space:
Rm -f /tmp/test.img
This will only work on a dedicated server or VPS. And, not on every VPS. Since they also differ in virtualization technology. Many hosters do not provide full-fledged virtualization (KVM, XEN) but containers (openVZ). There is no access to the kernel parameters, which means that it will not be possible to reset the cache. You will have to read and write to different files, or wait a few hours before the read test until the disk cache is overwritten with other data. It is also quite difficult to test the speed on a shared hosting, since you do not have root access there. But the dd utility is usually available to any system user, so you can check on it with SSH access.
To determine the disk write speed, you need to run the following command in the console:
sync; dd if=/dev/zero of=tempfile bs=1M count=1024; sync
The command writes a temporary file 1 MB in size 1024 times and the result of its work will be the output of such data
1024+0 records received 1024+0 records sent copied 1073741824 bytes (1.1 GB), 15.4992 s, 69.3 MB/s
To determine the disk read speed, you need to run the following command in the console:
The temporary file that was generated by the previous command is cached in the buffer, which will increase its reading speed by itself and it will be much higher than the actual reading speed directly from the hard disk itself. In order to get real speed, you must first clear this cache.
To determine the speed of reading from a disk from a buffer, you need to run the following command in the console:
Dd if=tempfile of=/dev/null bs=1M count=1024
Output of the previous command:
1024+0 records received 1024+0 records sent copied 1073741824 bytes (1.1 GB), 15.446 s, 69.5 MB/s
To measure the actual read speed from the disk, clear the cache:
sudo /sbin/sysctl -w vm.drop_caches=3
Command output:
vm.drop_caches = 3
We perform a reading speed test after clearing the cache:
Dd if=tempfile of=/dev/null bs=1M count=1024 1024+0 records received 1024+0 records sent copied 1073741824 bytes (1.1 GB), 16.5786 s, 64.8 MB/s
Performing a read/write speed test on an external drive
To test the speed of any External HDD, USB Flash Drive or other removable media or file system of a remote machine (vps / vds), you need to go to the mount point and execute the above commands.
Or, instead of tempfile, you can of course write the path to the mount point, as follows:
sync; dd if=/dev/zero of=/media/user/USBFlash/tempfile bs=1M count=1024; sync
You should also specify that the above commands use the temporary file tempfile. Don't forget to delete it after the tests are over.
HDD speed test using hdparm utility
hdparm is Linux utility, which allows you to quickly find out the read speed from your hdd.
To start measuring reading speed from your hard drive, you need to run the following command in the console:
sudo hdparm -Tt /dev/sda
Command output in console:
/dev/sda: Timing cached reads: 6630 MB in 2.00 seconds = 3315.66 MB/sec Timing buffered disk reads: 236 MB in 3.02 seconds = 78.17 MB/sec
That's all. Thus, we were able to find out the performance of our hard drive and give a rough estimate of its capabilities.
If there is something that you really do not want to face in your operating system, then this is definitely an unexpected failure of hard drives. With backup and RAID storage technology, you can get all your data back in place very quickly, but losing a hardware device can be a big budget hit, especially if you didn't plan on it.
To avoid such problems, you can use smartmontools. This is a software package for managing and monitoring storage devices using Self-Monitoring Analysis and Reporting Technology, or simply SMART.
Most modern ATA / SATA, SCSI / SAS drives provide a SMART interface. The purpose of SMART is to monitor the reliability of the hard drive, to identify various errors and respond in a timely manner to their occurrence. Smartmontools consists of two utilities - smartctl and smartd. Together they provide a powerful system for monitoring and warning about possible HDD failures in Linux. Checking the linux hard drive will be discussed in detail next.
The smartmontools package is in the official repositories of most Linux distributions, so the installation is reduced to executing a single command. On Debian and based systems, run:
aptitude install smartmontools
And for Red Hat:
yum install smartmontools
Now you can proceed to the diagnostics of the linux hard drive.
Check hard drive in smartctl
Find out first what hard drives connected to your system:
ls -l /dev | grep -E "sd|hd"
The output will be something like this:
Here - sdx is the name of the HDD device connected to the computer.
To display information about a specific hard drive (device model, S/N, firmware version, ATA version, SMART interface availability) Run smartctl with the info option and the name of the hard drive. For example, for /dev/sda:
smartctl --info /dev/sda
Although you may not pay attention to the ATA version, it is one of the most important factors when looking for a replacement device. Each a new version ATA is compatible with the previous ones. For example, older ATA-1 and ATA-2 devices will work fine on ATA-6 and ATA-7 interfaces, but not vice versa. When the ATA versions of the device and the interface do not match, the hardware capabilities will not be fully exploited. In this case, it is best to choose to replace HDD ATA-7.
Run a hard test disk ubuntu can be done with the command:
smartctl -s on -a /dev/sda
Here option -s turns on the SMART flag on the pointing device. You can remove it if SMART support is already enabled. The disk information is divided into several sections, In the section READ SMART DATA contains general information about the health of the hard drive.
START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment rest result: PASSED
This test can be passed PASSED) or not ( FAILED). In the latter case, failure is inevitable, start backup data from this disk.
The next thing to look for when diagnosing an HDD in linux is the SMART attribute table.
The SMART table records the parameters defined for a particular disk by the developer, as well as the failure threshold for these parameters. The table is filled in automatically and updated based on the drive's firmware.
- ID #- attribute ID, usually a decimal number between 1 and 255;
- ATTRIBUTE_NAME- Attribute name;
- FLAG- attribute processing flag;
- VALUE- this field represents the normal value for the state of this attribute in the range from 1 to 253, 253 is the best state, 1 is the worst. Depending on the properties, the initial value can be from 100 to 200;
- WORST- the worst value ever;
- THRESH- the lowest value value, after the transition, after which it is necessary to report that the disk is unusable;
- TYPE- attribute type, can be Pre-fail or Old_age. All attributes are considered critical by default, that is, if the disk fails the test for one of the attributes, then it is already considered unusable (FAILED), but the old_age attributes are not critical;
- UPDATED- shows the frequency of updating the attribute;
- WHEN_FAILED- will be set to FAILING_NOW if the attribute's value is less than or equal to THRESH, or to "-" if higher. In the case of FAILING_NOW, it is best to perform a backup as soon as possible, especially if the attribute type is Pre-fail.
- RAW_VALUE- value defined by the manufacturer.
Now you think yes smartctl good tool, but I do not have the ability to run it manually every time, it would be nice to automate the whole thing so that the program runs periodically and informs me of the results of the check. And it's possible with smartd.
Configuring smartd and smartctl for real-time diagnostics and monitoring
Real-time hdd diagnostics in linux is very easy to set up. First edit the smartd configuration file - /etc/smartd.conf. Add the following line:
nano /etc/smartd.conf
/dev/sda-m [email protected]-M test
- -m
- -M- frequency of sending emails. once - send only one message about disk problems. daily- send messages every day if a problem was found. diminishing- send messages every other day if a problem was found. test- send a test message when starting smartd. exec- executes the specified program to the place where the mail is sent.
Save changes and restart smartd. You should receive an email with the following content:
You can also schedule tests according to your own schedule, to do this, use the -s option and regular expression type "T/MM/DD/DN/HH", where:
- T- test type:
- L- long test;
- S- short test;
- C- movement test (ATA);
- O- offline (test).
The rest of the characters define the date and time of the test:
- MM- month of the year;
- DD- day of the month;
- HH- One o'clock;
- DN- day of the week (from 1 - Monday 7 - Sunday;
- MM, DD and HH- are indicated from two decimal digits.
A dot means all possible values, an expression in brackets (A|B|C) means one of three options, an expression in square brackets means a range (from 1 to 5).
For example, to perform a full check of a linux hard drive every weekday at 1pm, add the following line to smartd.conf:
DEVICESCAN -s (L /../../ / 13)
conclusions
If you want to quickly check the mechanical operation of a hard drive, view its physical condition, or perform a more or less complete scan of the disk surface, use smartmontools. Don't forget to scan regularly, you'll thank yourself later. Have you done this before? Will you do? Or do you use other methods? Write in the comments!
Translation source.
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