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Special Forums Hardware Filesystems, Disks and Memory Does vmstat -d give a count of actual physical writes/reads done to/from hard disk? Post 302315150 by otheus on Monday 11th of May 2009 04:39:14 PM
Old 05-11-2009
Well, if you're using Linux, you can look at the sysstat code, which probably does some kind of ioctl on the raw device, and so you could look at the Linux kernel, which might end up telling you that it counts the number of blocks sent to the IO controller for writing; whether or not that means the device actually wrote those blocks, I don't think one can say.

Now it could be that the disk and its controller keep track of a statistic and it's possible to get that value, but I doubt this is what sa/sysstat relies on. Further, I've written SCSI drivers before, and if this feature exists nowadays, it's not in the standard, meaning it's on a device-by-device basis.
 

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SYSSTAT(5)							Linux User's Manual							SYSSTAT(5)

NAME
sysstat - sysstat configuration file. DESCRIPTION
This file is read by sa1(8) and sa2(8) shell scripts from the sysstat's set of tools. It consists of a sequence of shell variable assign- ments used to configure sysstat logging. The variables and their meanings are: HISTORY The number of days during which a daily data file or a report should be kept. Data files or reports older than this number of days will be removed by the sa2(8) shell script. COMPRESSAFTER Number of days after which daily data files are to be compressed, either by gzip or bzip2. SADC_OPTIONS Options that should be passed to sadc(8). With these options (see sadc(8) manual page), you can select some additional data which are going to be saved in daily data files. These options are used only when a new data file is created. They will be ignored with an already existing one. FILES
/etc/sysconfig/sysstat AUTHOR
Sebastien Godard (sysstat <at> orange.fr) SEE ALSO
sadc(8), sa1(8), sa2(8) http://pagesperso-orange.fr/sebastien.godard/ Linux SEPTEMBER 2010 SYSSTAT(5)
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