Perform timings of cache reads for benchmark and comparison purposes. For meaningful results, this operation should be repeated 2-3 times on an otherwise inactive system (no other active processes) with at least a couple of megabytes of free memory. This displays the speed of reading directly from the Linux buffer cache without disk access. This measurement is essentially an indication of the throughput of the processor, cache, and memory of the system under test. If the -t flag is also specified, then a correction factor based on the outcome of -T will be incorporated into the result reported for the -t operation.
-t
Perform timings of device reads for benchmark and comparison purposes. For meaningful results, this operation should be repeated 2-3 times on an otherwise inactive system (no other active processes) with at least a couple of megabytes of free memory. This displays the speed of reading through the buffer cache to the disk without any prior caching of data. This measurement is an indication of how fast the drive can sustain sequential data reads under Linux, without any filesystem overhead. To ensure accurate measurements, the buffer cache is flushed during the processing of -t using the BLKFLSBUF ioctl. If the -T flag is also specified, then a correction factor based on the outcome of -T will be incorporated into the result reported for the -t operation.
The disk buffer is physically distinct from and is used differently than the page cache typically kept by the operating system in the computer's main memory. The disk buffer is controlled by the microcontroller in the hard disk drive, and the page cache is controlled by the computer to which that disk is attached. The disk buffer is usually quite small, from 2 to 32 MiB, and the page cache is generally all unused physical memory. While data in the page cache is reused multiple times, the data in the disk buffer is rarely reused.
This is from my notebook (Windows 7/Cygwin):
internal drive
external USB 2 drive:
This is from an Ubuntu on VirtualBox (on the external USB 2 drive):
hi all
i have a program in C (Unix Solaris 5.7) and i want to read a string from keyboard, but the "scanf" doesn´t reads spaces.
example:
....
char name;
....
printf("Enter your name: ");
scanf("%s",&name);
printf ("Your name is: %s", name);
and if i write Kevin Costner ... (4 Replies)
I would like to write shell/perl script which identifies the top unix processes that are performing high disk I/O's or/and writes
If any one knows the solution please help me?
-Swamy (0 Replies)
Guys,
Is there any UNIX command that captures the 'Unix process which is performing high disk I/O reads and writes'.
can you help me in this?
-Swamy (6 Replies)
Hi,
I am trying to find the reliability of 'vmstat -d' for showing the actual physical writes on sectors on hard disk.
Can anyone please tell me if the numbers in the "sectors" field under "read" or "write" headers show a count of the actual write commands sent to disk from the low level... (2 Replies)
After I using the search tool, I still can't find a solution that was related with my trouble.
My input file:
@HWI-ABC123_30DFGGDA:1:100:3:1234
ACGTAGTACCCGGGTTTTTTTTTAAAAAAA
+HWI-ABC123_30DFGGDA:1:100:3:1234
hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
@HWI-ABC555_30DFGGDA:1:100:3:1234... (14 Replies)
Hi,
I am in need of help on reading through a file(servernames.dat) which has a list of server names, while it reads each file name it has to connect to that server and run another script, once it has executed the script on one server, it has to go back to the list of servernames to get the next... (5 Replies)
I'm trying to performance tune the I/O of my web server, which is at 41.1% reads merged (If my math is correct), which seems a tad high to just be going along with the defaults. Will modifying read_ahead_kb affect the value of "reads merged" in diskstats? If not, what's a good way of tracking... (2 Replies)
Hey guys,
Does anyone know how to calculate total number of mapped reads for a certain region of a bam file using samtools flagstat?
I know to use flagstat for the whole bam file. but for a specific region of it... is there an option?
Tnx
---------- Post updated at 12:27 PM ----------... (1 Reply)
cleanwork /saswork removes sas orphanded processes in the saswork directory. Subdirectories under sasem are sas94, sas92 and sasworks .
I am getting the following error messages:
1.
'/usr/bin/sudo -S apt-get update <~/opt/SiM/pos/ps/db_auth.cfg... (4 Replies)
I have below script to read a file line by line. How can I ensure that the loop will stop after last line.
#!/bin/bash
while read -r mod ver tarball; do
echo $mod
done < taskfile.txt (4 Replies)