Posts

Showing posts from November, 2013

Stripped LVM (RAID 0) performance on a NAS system

Image
Now I am setting up a new NAS and to be able to decide if I should use Stripped LVM I did some measurements. Stripped LVM means the the data volume is spread across 2 physical disks and data reads and writes are executed in parallel to the two disks, so in theory this will duplicate the disks speed. However stripping has one disadvantage that if one of the disks fails then all data is lost, while with normal volumes, there are chances that from the functional disk it is possible to restore the data. The NAS has a Gigabit Ethernet LAN connection so in theory 125 MBytes/sec speeds can be achieved.

To do the tests I have set up two 200 GByte logical volumes on the LVM containing two 4 Tbytes physical disks, one stripped across the two disks and the other without stripping. First I measured the speed within the NAS, using the linux DD command:

On the normal volume:

>dd if=/dev/zero of=/media/data/Adatok/test bs=1M count=2000      2000+0 records in
2000+0 records out
2097152000 bytes (2.1 …

Speeding up NTFS file system access on Linux with a Windows virtual machine

Image
Summary:Ntfs-3g is not performing well, here are some measurements and a complicated way to have faster NTFS filesystem access on Linux.

Disclaimer: These tests were done on an Ubuntu 10.4 LTS installation, with the latest sw versions included in this Ubuntu distribution, but on the ntfs-3g site there are more recent versions of that ntfs-3g.

I wanted to do a backup of my Linux based NAS, to an NTFS formatted hard drive, which meant to copy around 4 TByte of data.

As the first step I built the disk into the NAS machine over a SATA connection and measured the drive speed:

>sudo hdparm -t /dev/sdf

/dev/sdf:
 Timing buffered disk reads:  432 MB in  3.01 seconds = 143.62 MB/sec

This looks good, this means, 4 TB/143MB ~ 7 hours of copy time.

Next I mounted the already formatted drive and did a copy test:

>sudo mount -t auto /dev/sdf2 /media/windows/
>dd if=/dev/zero of=/media/windows/test bs=512 count=390625
390625+0 records in
390625+0 records out
200000000 bytes (200 MB) copied, 94.6419 …