Frozen Industries

Keeping track of my drive failures, since April 2011.

Create a single, aligned partition on a drive larger than 2TB.

% sudo parted /dev/sdx
(parted)% mklabel gpt
(parted)% mkpart primary 1 -1

Just replaced my heavily used Ubuntu HTPC with a 6 watt AppleTV 2. Both run XBMC.

Specs of the old, silent HTPC:

• Intel Core 2 Duo E4300 1.8GHz w/2MB Cache
• Intel DQ965GF motherboard with passive chipset heatsinks
• Scythe Ninja passive CPU heatsink
• 4GB (2x 2GB DIMMS) ADATA DDRII 800 MHz memory
• 512 MB MSI N210-MD512H GeForce 210 PCIe 2.0 passive video card
• 40 GB Kingston SSDNOW V-series (Intel rebranded) SATA SSD
• 18x DL DVD+-RW Optiarc Ad-7170S 2MB Cache SATA optical drive
• Antec Sonata case
• Dual 120mm Yate Loon case fans
• Seasonic 330W power supply
• Ubuntu 10.04 AMD64 with XBMC

Video is just as smooth on the AppleTV as on the HTPC.

Screens I look at on a normal weekday:

• iPhone 4 (3.5″) (960 x 640)
• iPad (9.7″) (1024 x 768)
• Netbook (10.1″) (1024 x 600)
• Work MacBook (15.4″) (1440 x 900)
• Work Desktop (27″ + 24″) (2560 x 1440 + 1920 x 1200)
• Home Desktop (30″) (2560 x 1600)
• HTPC (42″) (1920 x 1080)

Tests are done across four 7200RPM SATAII drives on a PCI-X card sitting on a PCI (32-bit, 133MB/sec theoretical max) bus, probably the slowest bus configuration possible, and then again after being moved to a motherboard with dual PCI-X slots. Server is running Ubuntu 9.10 AMD64 Server.

Benchmark is a simple ‘dd’ sequential read and write.

write: dd if=/dev/zero of=/dev/md2 bs=1M
read: dd if=/dev/md2 of=/dev/null bs=1M

mdadm –create /dev/md2 –verbose –level=10 –layout=n2 –raid-devices=4 /dev/sd[ftlm]1

mdadm –create /dev/md2 –verbose –level=10 –layout=f2 –raid-devices=4 /dev/sd[ftlm]1

mdadm –create /dev/md2 –verbose –level=10 –layout=o2 –raid-devices=4 /dev/sd[ftlm]1

And more comparisons:

RAID1 (PCI)

write: 38.9 MB/s
read: 64.8 MB/s

Single Disk (PCI)

write: 59.4 MB/s
read: 71.9 MB/s

Have an LVM device left on your system from a drive that was removed before pvremove was run?

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$ sudo dmsetup remove /dev/mapper/removed-device

I wrote a short script that sends a Tweet whenver my Tivo HD starts recording a show. You can download it below. It runs best on a Linux computer that can constantly poll the Tivo.

Download: tivo_twitter.sh script

Results: http://twitter.com/30west

I passed 365 days of uptime on my Linksys WRT54GL v1.1 router. It’s running DD-WRT firmware, and sits on a large APC UPS. Total data transfer on the router’s WAN port is reported at 1,570,619 MB down/ 79,832 MB up.

LVM allows you to hot add devices to expand volume space. It also allows you to hot remove devices, as long as there are enough free extents in the volume group (vgdisplay) to move data around. Here I’m going to replace a 400 GB drive (sdg) with a 750 GB one (sdf) from logical volume “backup” on volume group “disks”. It does not matter how many hard drives are in the volume group, and the filesystem can stay mounted.

1. Partition and create a physical volume on the device

   1	$ sudo pvcreate /dev/sdh1

2. Add the new drive to the volume group

   1	$ sudo vgextend disks /dev/sdh1

3. Move all extents from the old drive to the new one (this step may take hours)

   1	$  sudo pvmove -v /dev/sdg1

4. Remove the old drive

   1	$ sudo vgreduce disks /dev/sdg1

5. Expand the logical volume to use the rest of the disk. In this case, another 350GB.

   1	$ sudo lvextend -l+83463 /dev/disks/backup

6. Expand the file system

   1	$ sudo resize2fs /dev/disks/backup

Scan a system for RAID arrays and save findings so the array reappears across reboots:

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# mdadm --detail --scan >> /etc/mdadm/mdadm.conf

Create a RAID5 array out of sdm1, sdj1, and a missing disk (all partitioned with raid-autodetect partitions)

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# mdadm --create /dev/md1 --level=5 --raid-devices=3 /dev/sd[mj]1 missing

Create a RAID1 array

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# mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sd[ts]1

Remove a RAID array

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2

# mdadm --stop /dev/md1
# mdadm --zero-superblock /dev/sd[ts]1

Replace a failed drive that has been removed from the system

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# mdadm /dev/md3  --add /dev/sdc1 --remove detached