Tuesday, June 2, 2009

AutoYaST and LVM striping

A less known fact of the AutoYaST LVM configuration is, that it can do striping too. The reason for that being less known might be, that I just documented it a few weeks ago, even though that feature was available since ages.
If you now say "I want that!!! What is it good for?" you can read this article. In a nutshell, with striping you spread the harddisk IO across multiple physical devices which increases the IO performance but also the risk of data loss, so never use that without a RAID system below.

How to use that in AutoYaST? Just configure the number of physical devices and the blocksize in KB like this:


<drive>
<device>/dev/data_vg</device>
<is_lvm_vg config:type="boolean">true</is_lvm_vg>
<type config:type="symbol">CT_LVM</type>
<partitions config:type="list">
<partition>
<filesystem config:type="symbol">ext3</filesystem>
<lv_name>my_data_lv</lv_name>
<mount>/data</mount>
<stripes config:type="integer">2</stripes>
<stripesize config:type="integer">4</stripesize>
<size>10G</size>
</partition>
</partitions>
<pesize>4M</pesize>
<use>all</use>
</drive>

That's the same like you would do without striping, except for those two keys:

<stripes config:type="integer">2</stripes>

which is the number of physical devices you use. And:

<stripesize config:type="integer">4</stripesize>

which is the size of a block in KB. So after writing 4kb the physical device will be switched.
That's all you need to activate striping on a logical volume.


happy striping - Uwe

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