[CentOS-docs] Updated How to Setup a Software RAID on CentOS 5
ned at unixmail.co.uk
Wed Apr 29 18:56:21 UTC 2009
Ed Heron wrote:
> From: "Phil Schaffner", Tuesday, April 28, 2009 5:36 PM
>> I have attempted to address all comments:
>> Give me your best shot! :-D
> There's always going to be an argument about whether to put /boot and swap
> on RAID. It's all about performance most of the time being slightly better
> versus stability in the event of device failure.
I can't think of a good argument for not having /boot on the raid1.
Presumably performance isn't an issue as the contents of /boot gets read
once at system boot (other than maybe fast booting performance, but
that's not really going to be an issue for a server running raid1, right?)
SWAP on raid0 is a bad idea as one drive failure may cause the system to
fail to boot. I guess SWAP on raid1 is the safe option. If SWAP
performance is critical, then maybe two independent non-raid partitions,
one at the start of each drive, and set to the same priority would be a
better solution (effectively giving stripped raid0 performance).
Presumably then a drive failure wouldn't prevent booting but would
result in a warning that one of the SWAPs was unavailable (assuming the
system could function fine with the size of the remaining SWAP)?
Hopefully someone can verify my logic here.
> What's the disaster recovery plan here?
> Obviously, if the second drive fails, there's no issue. Standard removal
> and eventual addition of replacement device(s).
> If the first drive fails, are we hoping the computer will boot off the
> second drive or are we moving the second drive to the first interface?
If grub is present on the mbr of both drives, then the system will
remain functional if *either* drive fails without any further
intervention. I would think this is the ideal.
> Is it outside the scope of this document to describe and test disaster
> recovery? I think it is. I'm just making a note to suggest a further
> complimentary page at some time in the future... (though, at this time, I
> am NOT volunteering to write it) Is there a wiki page todo list somewhere?
I would be in favour of extending the current page to include
testing/recovery information in the event of a drive failure. If the
information is not specific to only raid1, then maybe a separate page is
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