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Re: Speed Problem Copying Files

On 5/13/19 1:30 AM, Lothar Schilling wrote:
# cat /etc/debian_version


# uname -a
Linux [my.server.com] 4.9.0-9-686-pae #1 SMP Debian 4.9.168-1
(2019-04-12) i686 GNU/Linux

As other readers have noted, you are running 32-bit Debian GNU/Linux. It should not matter for what we're doing, but...

# lsblk
sda      8:0    0   3,7T  0 disk
├─sda1   8:1    0   476M  0 part /boot
├─sda2   8:2    0  93,1G  0 part /
├─sda3   8:3    0  18,6G  0 part [SWAP]
└─sda4   8:4    0 931,3G  0 part /daten

So, your boot, root, swap, and data are all on a 4 TB drive. I put my boot, swap, and root on a small "system" disk (SSD or USB flash drive) and my bulk data on large "data" disks (HDD; preferably RAID). Again, it should not matter; but...

# mount | egrep 'sd[a-z]'
/dev/sda2 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)
/dev/sda4 on /daten type ext4 (rw,relatime,data=ordered)
/dev/sda1 on /boot type ext4 (rw,relatime,data=ordered)


# df | egrep 'sd[a-z]'
/dev/sda2       95596964  2241952  88455840    3% /
/dev/sda4      960185376 41249236 870091648    5% /daten
/dev/sda1         463826    57063    378296   14% /boot


# time dd if=/dev/urandom of=test bs=1M count=100 conv=fsync
100+0 Datensätze ein
100+0 Datensätze aus
104857600 Bytes (105 MB, 100 MiB) kopiert, 192,778 s, 544 kB/s
real    3m12,781s
user    0m0,000s
sys     0m1,480s

As you have redacted your prompt, I must assume your current working directory was within a file system on /dev/sda?

Write performance is bad. But, now that you have a good test case for trouble-shooting. :-)

# echo 3 > /proc/sys/vm/drop_caches && time dd if=test of=/dev/null
204800+0 Datensätze ein
204800+0 Datensätze aus
104857600 Bytes (105 MB, 100 MiB) kopiert, 0,600354 s, 175 MB/s
real    0m0,675s
user    0m0,048s
sys     0m0,340s

Read performance is questionable:

1. The file may be small enough to fit entirely within the drive cache (e.g. 128 MB drive cache). If so, I would have expected interface speed (e.g. ~600 MB/s for SATA 3).

2. You forgot to specify 1 megabyte blocks 'bs=1M'. dd defaults to 512 byte blocks. The drive probably uses 4 kB blocks. Small blocks reduce performance for large files.

3.  Until we figure out the write problem(s), everything else is suspect.

Consider getting a power supply tester and checking your power supply. Computers behave very strangely when one power supply rail goes out but the others keep working. I have an Antec, but I believe it is out of production:


Download a bootable memory diagnostic tool, write it to media, boot it, and run it for at least an hour. Some people have criticized the tool I use, so I won't make any recommendations. If the tool finds memory problems, re-seat your memory modules and try again.

Download the diagnostic toolset from your disk drive manufacturer's web site, write it to media/ install it (Windows may be required), and run all the non-destructive tests. If there are problems:

* Re-seat the drive power cable and try again.

* Re-seat both ends of the drive data cable and try again.

* Substitute another drive data cable and try again.

* Use a different drive port on your motherboard or interface card and try again.

Please reply with your findings.