Where to set readahead: LVM, RAID devices, device-mapper, block devices?

You want to set readahead to tune the performance of you disk reads and you find that in your server there are several levels of devices, block devices, RAID devices, then LVM with device-mapper, etc.

You can set the readahead in any of them, which one is the right one?

I came up with this Stackoverflow question: https://serverfault.com/questions/418352/readahead-settings-for-lvm-device-mapper-software-raid-and-block-devices-wha

And i decided to do some tests to prove what wojciechz was saying, and he is right, let me show you:

My setup is a server with RAID10 and LVM with a /db partition mounted on the logical volume

# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md127 : active raid10 sdj[7] sdi[6] sdh[5] sdg[4] sdf[3] sde[2] sdd[1] sdc[0]
3906525184 blocks super 1.2 512K chunks 2 near-copies [8/8] [UUUUUUUU]

# pvdisplay
--- Physical volume ---
PV Name /dev/md127
VG Name vg1
PV Size 3.64 TiB / not usable 0
Allocatable yes
PE Size 4.00 MiB
Total PE 953741
Free PE 489746
Allocated PE 463995
PV UUID KH4RjS-lgAN-2OdI-hiYQ-HuR1-naDM-nSmc5S

# mount | grep db
/dev/mapper/vg1-db on /db type ext4 (rw,noatime,nodiratime,discard,stripe=512,data=ordered)

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Installing Google Chrome in Debian Lenny

If you are thinking about installing the newest version of Google Chrome in Debian Lenny, don’t waste your time, you can’t (actually, you can but i don’t think you want to compile every package dependency).

The Google Chrome team is not supporting Debian Lenny and the latest package version supported is Google Chrome 12.

The package depends on other packages that are not in Debian Lenny anymore, there isn’t even a backport package for some of them. So, if you want this browser in the “super stable” Lenny version, you need to be satisfied with the version 12.

And if you really need the newest version, upgrade to Debian Squeeze. The installation in Squeeze is pretty straightforward, just install the .deb and resolve the dependencies:

dpkg -i google-chorme-latest-version.deb
apt-get -f install

I couldn’t find older packages in the Google Chrome page, so here you have a link to the 12 version:

Arch AMD64: http://linuxfreedom.com/hacktolive/repo/archive/pool/main/g/google-chrome-stable/google-chrome-stable_12.0.742.112-r90304_amd64.deb

Arch i386: http://linuxfreedom.com/hacktolive/repo/archive/pool/main/g/google-chrome-stable/google-chrome-stable_12.0.742.112-r90304_i386.deb