Tuesday, 30 March 2010

Fake RAID in Linux: Sony Vaio Z11 series with 4x64 SSD

Some of the laptops in the market, like the Sony Vaio Z-series 2010 (e.g., Z11) come with a RAID hard drive that looks like it's 4x64GB, but it actually behaves more like a 2x128GBs configuration. Sony has engineered its own software layer for this, and this hasn't been implemented in Linux at the time of this writing (20100330). Since Linux cannot recognize this kind of Fake RAID at boot time, it will cause problems when trying to install Ubuntu with default options (other distros may have slightly different behaviours).
https://lists.launchpad.net/sony-vaio-z-series/msg01145.html
The good news is that there *are* workarounds, like the dmraid module, which can be found here:
https://help.ubuntu.com/community/FakeRaidHowto

But for the Z11 sony-vaio-z-series case, it's been reported that what *does* work is to follow the instructions in this youtube video:
http://www.youtube.com/watch?v=-x2rZe2Z9as

This will set up an Ubuntu Karmic with a soft RAID 0, with the Fake RAID disabled by the BIOS.

Other users have commented that disabling the onboard RAID is probably the best solution, even once Linux dmraid supports the chipset. The argument is that Linux software will often give at least as good performance as most onboard 'RAID controllers'.

There is a caveat to the RAID0 configuration: losing any drive can potentially destroy all your data. So another suggestion is to use
RAID10 (or RAID5) for speed/redundancy, or alternatively, to add all the drives to a linear LVM volume, giving you access to all the
space. This means you only lose what's on a single drive if it dies.

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