On 07/14/2015 06:13 AM, David Timms wrote:
On 14/07/15 07:42, jd1008 wrote:
On 07/13/2015 03:13 PM, Patrick O'Callaghan wrote:
On Mon, 2015-07-13 at 13:50 -0600, jd1008 wrote:
I started a tar command from
one external eSATA drive (ext4), connected to eSATA port,
out to a USB flash drive (with vfat). The USB stick is touted
to support 50MB/s write, 160MB/s read.
Have you actually measured its real write speed for large files? Try
something like:
time dd if=/dev/zero of=/the/usb/drive count=1000 bs=1M
You might be surprised.
poc
As I just replied with the actual read/write performance data
on this USB 3.0 SUperTalentExpress Drive (256GB), I am
much more surprised by the fact that while tarring a large
dir to it from a fast eSATA drive, the system becomes nearly
unusable!!!
So, if this "shtick" is so slow, why is writing to it killing the response
time for everything else?
I see the same sort of issue (F21, cinnamon desktop). If the disk write
or read is getting "backed up" with a queue of info, then that should
mean the desktop UI is more responsive, since the CPU is idle. But it
doesn't seem to work that way. It quite often seems to be waiting on a
large disk IO to complete.
On mine, possibly having once connected to a windows7 machine and copied
a mpg file from it to mine, but leaving the nemo window open might be a
trigger. And an hour after boot, the prelink operation runs (again,
should be set for tinniest priority, and rest of OS should be normal
especially given / is on an SSD (with modified time writing disabled).
Love to hear some things to try...
I wish I knew ...
I find that the desktop kernel and scheduler are tuned more
to server operations where FS buffers for all the threads are
given priority as the desktop is either non-existent or not in operatio.
memory is used mostly for these buffers (aka pagecache).
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