New subject: [opensuse] Of software RAID on SUSE Linux

30 Nov 2008

      On Sunday 30 November 2008, you wrote:
...
On Thu, Nov 27, 2008 at 5:50 PM, Tero Pesonen 
 wrote:
...
Of course, a RAID won't help
against other kinds of data loss, such as the power supply's
failing and killing other components with some mighty spike; or
from fire, or flood, or what ever. That is OK. That's why I backup.
Are you using a UPS?
I've never used a UPS device before for a desktop at home. I've been 
thinking of acquiring one for the new system -- the one with the 
RAID -- so as to avoid problems in case of a black-out. I've read that 
this is recommended with RAIDs as the disks need to keep in sync and 
no-one knows what'll happen when they all power down unexpectedly. So 
having the system go down gracefully is preferred. I have not yet 
looked at products or prices. But if I had a UPS for my home box, and 
the power went out, and the UPS went to work for a short period of 
time, how would my system know to "init 0" or something like that 
during the time the UPS would be able to feed it?

Do you have one, and if so, how does your setup work?
...
...
In other words, may I combine disks from
different manufacturers, with different specs, etc. without
affecting the RAID somehow negatively?
It is OK to mix manufacturers and capacities. It is good to mix discs
with different manufacture dates. This makes it less likely that the
discs will fail at the same time. But I would not mix buses, spindle
speed or cache size because I would not want to thrash one disc while
leaving the other one idle.
OK.
...
So, while you can mix discs, I bought an identical pair of hard discs
for my RAID 1. Using a pair of identical discs takes the guesswork
out of building a RAID. And I am satisfied with the result.
I guess two might suffice for me, too. Two identical Seagate ES.2 SATA's 
might work. They're specsed by the manufacturer for 24h use, for 
whatever that is worth (I always run my desktop 24h/d, and keep KDE up 
for months at time... so the disks spin a good deal. This is mostly 
because the OS-disks cannot be spinned down with hdparm for more than a 
few seconds due to the kernel's constantly flushing them. So, at night 
they are merely idling away at 7200rpm.)

I prefer not to turn the power on and off too much, as doing so seems 
the most efficient way for killing modern-day crappy PC components. 
Keeping the thing running seems to provide the most stable system.

I've only experienced one power cut on my home box over the past 10 
years. Luckily, that did not cause any fs errors, and reiserfs 
recovered from it with a boot-time fsck (that did quite a bit of work, 
though) without leaving any problems even though the disk had been 
writing when the power was cut.
...
...
On the other hand, replacing disks later with larger capacity ones
will cause no problem as they only need to meet the minimum size
criterion. Hence, I could replace them one-by-one such that each
new disk, replacing a removed old one, is first let to fully
integrate/reconstruct; finally, after all disk have been replaced,
I could enlarge a partition or two, for example, as allowed by the
new shared minimum, thus increasing the capacity of the virtual
device that is being RAIDed.
Remember to back up before experimenting.
Of course. Thanks to my rigorous habit of backing-up, despite hard drive 
failures, I have never really lost any important data.
...
You might want to look at using LVM rather than expanding partitions.
I'll do that. Thanks for the tip!
...
My System
I have a three disc system. I have one disc for the OS. And I have a
matched pair of Seagates in a RAID 1. The OS disc is a throwaway
disc. In other words, if something happens to it, I can just buy a
new disc, build a new install of openSuSE and be on my way. I have no
personal data on that disc. All of my data is on the RAID 1. And I
have a separate mount point for my stuff that does not overlap with
any standard Linux mount point such as /home or whatever. So the
biggest risks to my data are a double hardware failure or operator
error.
That seems like a good strategy. I will have to consider that kind of 
approach too.
...
I also have a removable hard drive with the same capacity as my RAID
that I use for backing up.
Mike
Thanks for your comments!
Tero Pesonen
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Re: [opensuse] Of software RAID on SUSE Linux

Tero Pesonen

Carlos E. R.

James Knott

Michael Mientus

Tero Pesonen

Carlos E. R.

JB2

Carlos E. R.

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participants (5)