[lug] RAID installation on Fedora 6 Zod

[Dan Ferris]

We use Linux software RAID heavily at work and have extremely good luck 
with it.  I prefer it to the 3ware type cards as long as I have SCSI or 
SATA drives.  The ATA seems to work ok, but not nearly as well as SATA.

However..

Having used Solstice Disk Suite/Solaris Volume Manager and FreeBSD GEOM, 
the Linux software RAID implementation is a joke.  On a Sun box, to make 
the root partition a mirror is as easy as doing metainit on a few 
slices, metaroot on the root slice and then a reboot then attach the 
second slice.  On FreeBSD it's as easy as setting the geom debug flags 
and going a gmirror on the desired partition, changing fstab and 
rebooting.  With Linux the same operation requires either a reinstall or 
a lot of trouble to copy data from one disk to another.

Also Sun makes hot swapping disks SO much easier than in Linux, but I 
digress.

Solaris and FreeBSD definatly have the right idea.  The Linux Software 
RAID needs to play some catchup.  There is no reason in my mind why it 
can't be a few simple steps to set up RAID.

Hey Nate, what do you guys do with the Sun system disks?  Obviously for 
data, you would use something like an EMC or Hitachi array with 
redundant active/active controllers, redundant power supplies, redundant 
fans, etc.  In our V240s and T2000s there is no hardware RAID.  You have 
to use Solaris Volume Manager for mirroring and the drives are easily 
hot swappable.  I also know that the E450 and E450R have no hardware 
RAID either.  I'm not sure about the higher end Sun hardware.  I never 
got to play much with the V1280s we had at Webex.

Dan

Dan

Sean Reifschneider wrote:
> On Fri, May 11, 2007 at 01:44:48PM -0600, Nate Duehr wrote:
>   
>> Linux needs to catch up to that!
>>     
>
> Linux software RAID has done this for at least a decade.  It's had to,
> because of the possibility that SCSI discs will move around when devices
> are added or removed.  This is why there is the "Linux RAID autodetect"
> partition type.  The system will look at those partitions and use the
> RAID meta-data on them to reconstruct RAID arrays, even if the drives have
> moved around.
>
> The 3ware cards also store meta-data on the drives and can deal with drives
> moving around.  Of course, this means that you can't just take an existing
> drive with data on it and have the RAID mirror it, because the meta-data is
> stored in the drive data area.  Ditto for the software RAID.  I know in the
> software RAID, it's stored at the end of the partition, so you can just
> resize the file-system a bit smaller, if supported, and RAID it after that.
>
> Sean
>   

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