steve0961
August 13th, 2010, 06:02 PM
I recently set up a 3 TB software RAID 5 array using Ubuntu 10.04 on 3 WD 1.5 TB green hard drives. All 3 drives were first run through the WD Data Lifeguard Diagnostic extended test and passed. The OS is installed to a 32 GB SSD and the RAID 5 array will be used as file server. I used the Palimpsest disk utility to set the array up (which uses mdadm) because I prefer using a GUI when it’s possible to. The array took ~8 hours to build and after I figured out how to fix a problem with the partitions being misaligned (due to the stripe size), I finally got the array partitioned and ready for usage. I ran the read benchmark test in the disk utility and got speeds basically at what I was expecting, an average of 136.5 MBps. I ran out of onboard SATA ports with the new array installed, so I have to copy over all the data I want on the array from the old 1 TB drive via an external USB enclosure. When I started the transfer (~300 GB) it zoomed through the first 700 MB or so fairly quickly, and then came to a screeching halt. It would then only write 50-100 MB at a time then pause for a few seconds. It kept repeating this process and I gave up after 5 GB.
I then tried to narrow down what the problem is by copying a ~6 GB folder from the external drive to the SSD that the OS is installed on. It zoomed right through the transfer at a steady 30-50 MBps. When I tried to copy the folder from the SSD to the RAID 5 array, it did the exact same thing as before (zoom through the first 700 MB and then go extremely slow). I then decided to delete the partition and the partition table from the array entirely and run the read/write test in the Disk Utility. Here are the results:
http://imgur.com/WNDd4.png
I don’t understand how the write speeds can be this bad. I then reformatted the array and tried again with similar results. I checked the system monitor with the transfer running and nothing is maxing out the CPU or RAM, nor are any of the relevant processes doing anything out of the ordinary. I was told on a different forum that nautilus is a dependency of the Palimpsest disk utility and to try a different file manager. I downloaded and installed the Dolphin file manager and it gave the same results. I’m at a loss of what to do here; I can’t even think of what else the problem could be. Any help would be greatly appreciated.
I then tried to narrow down what the problem is by copying a ~6 GB folder from the external drive to the SSD that the OS is installed on. It zoomed right through the transfer at a steady 30-50 MBps. When I tried to copy the folder from the SSD to the RAID 5 array, it did the exact same thing as before (zoom through the first 700 MB and then go extremely slow). I then decided to delete the partition and the partition table from the array entirely and run the read/write test in the Disk Utility. Here are the results:
http://imgur.com/WNDd4.png
I don’t understand how the write speeds can be this bad. I then reformatted the array and tried again with similar results. I checked the system monitor with the transfer running and nothing is maxing out the CPU or RAM, nor are any of the relevant processes doing anything out of the ordinary. I was told on a different forum that nautilus is a dependency of the Palimpsest disk utility and to try a different file manager. I downloaded and installed the Dolphin file manager and it gave the same results. I’m at a loss of what to do here; I can’t even think of what else the problem could be. Any help would be greatly appreciated.