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Having trouble installing a piece of hardware? Want to know if that peripheral is compatible with Linux?

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Old 09-11-2007, 04:24 AM   #16
tux_addict
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Sorry, I should have pointed out that it was a hard disk on a different machine, so it can't be the cache...
 
Old 11-26-2007, 05:06 AM   #17
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The learning never stops!

For reasons we needn’t get into, I recently commented out this line in my /etc/fstab file:

Quote:
/dev/sda /media/sda vfat rw,user,noauto,sync 0 0
so it now reads:

Quote:
# /dev/sda /media/sda vfat rw,user,noauto,sync 0 0
Now when I copy anything to my flash disk it’s done in ... a flash! For instance, I just copied a 14 MB file, which previously would have taken several minutes to copy from my hard disk to flash disk, in less than 3 seconds. The KDE progress dialog almost didn’t have time to come up! I could hardly believe it.

So, that dismisses my theory that (a) copying files to flash disk in Windows is much faster than it is in Linux (if anything, Linux seems faster – I'll have to test it), and (b) copying from a Linux filesystem such as reiserfs to the vfat system is slowed down by the need for some kind of conversion from one filesystem to the other.

So what does this mean? I have my own theories regarding block devices and HAL, which may or may not be wide off the mark. But that is for you gurus out there to say. What exactly is going on here? (My usb version is 1.1; I guess 2.0 would knock my socks off).

P.S. I must admit that the slow copying (or moving) of files from hard disk to flash disk was becoming a real show-stopper for me. Creating a /dev/sda entry in /etc/fstab was a practice I carried over from my 2.4 kernel days. To think that I was reluctant to migrate to the 2.6 kernel because it was too “bleeding edge” (thanks a lot Patrick Volkerding )!
 
Old 11-26-2007, 05:16 AM   #18
jschiwal
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Type in "mount" by itself and see what mount options the system used. It was probably the "sync" option that caused the problem. However, the speed you are seeing are probably writing to the cashe. It can still take a long time for the flash memory to catch up.

Code:
/dev/sdb1 on /mnt/xmas type vfat (rw,noexec,nosuid,nodev,noatime,flush,uid=1000,gid=1000,fmask=117,dmask=007,utf8,shortname=lower)
For flash memory, you want the "noatime" option to reduce the number of accesses. It will speed things up and increase the life of the memory.

Last edited by jschiwal; 11-28-2007 at 02:17 AM.
 
Old 11-29-2007, 03:19 AM   #19
tux_addict
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Disk caching

Quote:
the speed you are seeing are probably writing to the cashe.
To test jschiwal's theory, I picked a random file and copied it to my flash disk. As you can see, it took just a minute and a half to copy the fairly large (48 MB) file. Previously, this would have taken an hour or more!
Quote:
me@tuxilla:~$ du -h AdobeReader_enu-8.1.1-1.i386.deb
48M AdobeReader_enu-8.1.1-1.i386.deb
me@tuxilla:~$ time cp AdobeReader_enu-8.1.1-1.i386.deb /media/disk/



real 1m34.282s
user 0m0.016s
sys 0m1.264s
I doubt that caching is the explanation for the increase in speed. And I did eject the flash disk immediately after copying was completed to establish that there wasn’t anything going on in the background.
P.S. I shall test using the old method, with the noatime option and without sync. I doubt that it will make an appreciable difference, but there’s only one way to find out!
 
  


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