[Bug 271772] Re: iostat -k units are wrong when using large blocks

Jean-Baptiste Lallement jeanbaptiste.lallement at gmail.com
Tue Oct 14 22:34:24 BST 2008

My mistake, iostat is right. What iostat calls a block is a _physical
sector_ and this is not the same as a filesystem block.

Also from the FAQ:
3.4. I don't understand the output of iostat. It doesn't match what I expect it
to be...

By default iostat displays I/O activity in blocks per second. With old
kernels (i.e. older than 2.4.x) a block is of indeterminate size and therefore
the displayed values are not useful.
With recent kernels (kernels 2.4 and later), iostat is now able to get disk
activities from the kernel expressed in a number of sectors. If you take a
look at the kernel code, the sector size is actually allowed to vary although
I have never seen anything other than 512 bytes.

In my case hdparm returns
LBA48  user addressable sectors:  488397168
device size with M = 1024*1024:      238475 MBytes (ie 250059161600 bytes)

sector size = 250059161600 / 488397168 = 511.9996

** Changed in: sysstat (Ubuntu)
       Status: Confirmed => Invalid

iostat -k units are wrong when using large blocks
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