## HDD Spindown on Arch Linux

From hdparm's man page on the CLI parameter -S:

Put the drive into idle (low-power) mode, and also set the standby (spindown) timeout for the drive. This timeout value is used by the drive to determine how long to wait (with no disk activity) before turning off the spindle motor to...

## Improving the Speed of Software Raid on Linux (Read/Write/Resync)

### Speeding up the write access of a RAID array

echo 32768 > /sys/block/md0/md/stripe_cache_size


Source: Stackoverflow

### Speeding up RAID1 array rebuild

With

echo 50000 > /proc/sys/dev/raid/speed_limit_min
echo 200000 > /proc/sys/dev/raid/speed_limit_max


the resync speed went from 1M/sec to about 25M/sec:

cat /proc/mdstat

Personalities : [raid1]
md1 : active raid1 sdb3[0] sda3[1]
...

## Adjust Spindown Time for HDDs on Mac OS X

If you want to adjust the spindown time of the hard disk drives of your Mac OS X based computer, you can simply run the following command (which will set the spindown from the default 10 minutes to 30 minutes for all HDDs on your system):

pmset -a spindown...

## iSCSI on Ubuntu Linux

iSCSI is a software system (may be implemented in hardware) to mount remote block level devices locally. It does not provide a remote filesystem and thus is independent of the filesystem you might want to use on top of it.

iSCSI Target : PC that offers a block device to be...

## Sketch of an Advanced HDD / Partition Setup with high availability (mdadm software raid), encryption (dm-crypt) and high flexibility (lvm volume management)

Recently I found an interesting comment on an article about Fedora 16 maybe using btrfs as default file system: The author Vanger explained his current hard disk / partiton setup on a server and how he hopes to get a more efficient system with btrfs. More than the outlook...

## Secureley Erase Data

I have an old hard disk and I want to waste it. So I want to make sure there is no data left on the device:

• shred
• wipe

Overwrite the hard disk /dev/sdd using 1 run:

sudo shred -vn 1 /dev/sdd


A fast alternative:

sudo sh -c 'cryptsetup -d /dev/urandom -c aes-xts-plain...

## Remove the 5% root quota of an ext2 / ext3 partition

Usually 5% of the storage of an ext2 or ext3 volume are reserved for the root user. You can use tune2fs to make that space available to other users!

tune2fs -m 0 /dev/sdb1


Only do this for non-system partitions (as you might need the "root quota" to recover from full...

## Solve Boot Problems: The Kernel Did Not Find the Root Partition Using its UUID

On startup the system hung because the root UUID was not found. http://ubuntuforums.org/showthread.php?p=9020811#post9020811

So when I ran sudo blkid — executed from a live cd — it didn't show the root partition (all other partitions UUIDs were listed).

But tune2fs showed me its UUID

sudo tune2fs -l /dev/sda2


So I tried...

## Find out UUID of your Partitions

Run blkid:

blkid
/dev/sda1: UUID=”1c9e4ae2-0ddc-4e3c-8758-4cdd6c90407a” SEC_TYPE=”ext2″ TYPE=”ext3″
/dev/sda5: UUID=”a647ea33-74ee-4123-84bf-7edc32e2e39b” TYPE=”swap”

...

## Check Health of Software-RAID using mdadm

This article is about the data consistency health of your Raid. To check the physical health of the HDDs please use smartmontools to check the SMART status of your hard drives.

The simplest possibility to find out something about the status is to read the content of the special file...

## Use smartmontools to monitor S.M.A.R.T. status of your HDDs

The S.M.A.R.T. status is not a perfect measure of your hdd health but it can sometimes provide pre-failure notification. Here is how to check the S.M.A.R.T. status on Ubuntu:

Install the smartmontools using:

sudo aptitude install smartmontools


To display all the S.M.A.R.T. information for an IDE drive, run

sudo smartctl...