At 00:48 11.02.00 -0800, Andre Hedrick wrote:
>> Is there a good way to mirror Root disks.
>>
>> Is RAID-1 only options for mirroring under Linux or something else is
avialable.
>> If RAID-1 is the only option, how safe, fault tolerant it is.
>>
>> I fear setting up RAID for root, as any problem with RAID may make
system unbootable. Any
>> comments. suggestions links on Root disks mirroing ????
>Do hardware RAID..........ATA or SCSI but that is you only bet.
Granted - Hardware Raid is probably the most stable and professional
solutin - it's not the only one however:
You CAN have software raid for every part of your disk, including /.
A few pointers on software raid:
* have a look at the howto on http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
* You want to use the raid 0.90 code available as patches for 2.0 and 2.2
kernels, not the code included in the kernel tree
* With the 0.90 raid code, / on raid (any type - 0 / 1 / 4 / 5 work equaly
well) is no problem, the raid arrays get initialized by the kernel on
bootup and can be mounted just like any other device.
* Swap on raid is currently problematical - I think background
resynchronisation of mirror drives conflicts with use as swap; if you
ensure that no resynchronisation takes place while the device is used as
swap, it should work. Swap on raid would only make sense for mirror or
raid5 to gain reliability.
The only bit of configuration that's still a bit tricky is where to keep
the stuff needed by the bootloader to get a kernel into memory; usually the
stuff stored in /boot for lilo configurations. There are several ways of
dealing with /boot stuff:
* have a seperate non-mirrored /boot1, /boot2 etc. on each of the disks
containing mirrors of your / filesystem, have lilo write startup info to
each disk by having a seperate lilo.conf for each disk.
* have /boot on a raid1 mirror and use a patched version of lilo (patch by
redhat available in the redhat 6.1 source stuff). The patched lilo can
handle raid1 mirror devices and will make each of the devices in a mirror
bootable.
As for stability: The linux raid 1/4/5 code can handle failing disks
without requiring user interaction; you have to be careful with your setup
however - some errors have to be avoided to allow continued operation in
case of a drive failure:
* Don't put two parts of a raid device on the same IDE bus (master/slave)-
chances are that a failing master drive will take a slave on the same cable
with it, causing two drives to fail at the same time -not good. Besides, it
wont help performance either.
* If you're using SCSI, be careful which controllers / drivers you use -
some drivers don't handle failing disks well at all and will lock up your
system or slow it to a crawl by stubbornly trying to access the dead disk
and resetting the bus on failure indefinitely if a disk goes down.
Bye, Martin
"you have moved your mouse, please reboot to make this change take effect"
--------------------------------------------------
Martin Bene vox: +43-316-813824
simon media fax: +43-316-813824-6
Andreas-Hofer-Platz 9 e-mail: mb@sime.com
8010 Graz, Austria
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