# graid -- new software RAID implementation in 9-CURRENT



## mav@ (Mar 25, 2011)

New RAID GEOM class, that is going to replace ataraid(4) in supporting various BIOS-based software RAIDs, was committed to 9-CURRENT. Unlike ataraid(4) this implementation does not depend on legacy ata(4) subsystem and can be used with any disk drivers, including new CAM-based ones (ahci(4), siis(4), mvs(4), ata(4) with `options ATA_CAM`). To make code more readable and extensible, this implementation follows modular design, including core part and two sets of modules, implementing support for different metadata formats and RAID levels.

Support for such popular metadata formats is now implemented:
Intel, JMicron, NVIDIA, Promise (also used by AMD/ATI) and SiliconImage.

Such RAID levels are now supported:
RAID0, RAID1, RAID1E, RAID10, SINGLE, CONCAT.

For any all of these RAID levels and metadata formats this class supports full cycle of volume operations: reading, writing, creation, deletion, disk removal and insertion, rebuilding, dirty shutdown detection and resynchronization, bad sector recovery, faulty disks tracking, hot-spare disks. For Intel and Promise formats there is support multiple volumes per disk set.

Testers are welcome.


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## leoandru (Oct 1, 2011)

Shouldn't 
	
	



```
option GEOM_RAID
```
 be part of the GENERIC kernel? Seeing ataraid(4) was replaced I no longer got /dev/ar* device node for BIOS RAID volumes.

Had to *kldload geom_raid* to create /dev/raid volumes for installing FreeBSD 9.0-BETA3. Then added a line to /boot/loader.conf to load it at boot.


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## mix_room (Oct 3, 2011)

How is the backward compatability? Do I need to rebuild my soft-raids, or will they still run? What is the proposed upgrade strategy?

I am assuming gmirrors will not be affected, only the mentioned soft-raids (/dev/ar0 and similar)


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## olav (Oct 3, 2011)

I'm currently creating a new server with FreeBSD 9 BETA3 (Will be upgraded to 9-Stable soon). I've yet only installed and not configured a disk mirror. I've thought to use gmirror, what advantages are there by using graid? Is it faster? More reliable? New features?
Why should I not depend on the legacy ata(4) subsystem if it works? I'm one of those who says _if it works, don't fix it_ 
I'm really happy with gmirror, but if there are one or more real advantages to use graid, I will help test it


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## leoandru (Oct 3, 2011)

mix_room said:
			
		

> How is the backward compatability? Do I need to rebuild my soft-raids, or will they still run?



I'm using Intel SATA software RAID and I didn't have to rebuild my volumes, they still run. Instead of */dev/ar0* for the first raid array you'll now have */dev/raid/r0* and so on. With the new ahci(4) drivers there is also an appreciable improvement in read/write performance.

As for upgrading I guess you will need to modify /etc/fstab if your aren't using ufs labels or ids for mounting and you need 
	
	



```
geom_raid_load="YES"
```
 in /boot/loader.conf for now, unless its added to GENERIC kernel. graid(8) is the utility to manage the raid volumes.


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