[CentOS] More than 2TB RAID...

Peter Kjellstrom cap at nsc.liu.se
Wed Jan 28 16:20:32 UTC 2009


On Wednesday 28 January 2009, John Doe wrote:
> > > Yes, that's the plan but, the thing is to be able to run the
> > > utilities... I need either to make a live CD with the HP tools
> > > installed, or a "temporary OS with the tools... First try will be to
> > > create a RAID6 on 3 disks (=1 TB, so no grub problems), install the OS,
> > > run HP ACU, extend the RAID to the 12 disks, and create the logical
> > > disks... If first try fails, second try would be to use a temporary USB
> > > disk to install a temporary OS.
> >
> > This sounds much better to me. Invest 30 min. and install a centos-5 to a
> > 4G usb-stick. Put hpacucli and hpaducli on it and then you can configure,
> > manage and diagnose any server you want.
>
> I meant RAID6 on 4 disks of course... ^_^
> I could install and boot, but the CLI version of the ACU is a bit
> intimidating... And long and complex command lines, without command history
> is really painful.

True, that's why you run hpacucli from the linux shell :-)

This way bash (or whatever you use) will save the history.

> Anyway, I managed and am currently extending the array 
> to the 12 disks...  It seems that it is going to take around 3 days! Maybe
> because the cache battery is not fully charged and so the writes are not
> cached... After that, I need to reduce the "boot" logical disk down to a
> dozen of GBs. And then, I need to create the other(s) logical disk(s).

I think a sane end config is one logical drive for the OS (further chopped up 
with a ms-dos partition table) and one large logical drive for data (possibly 
chopped up with a gpt partition table or lvm).

> > > As for the logical disks sizes, we would go with
> > > something like 5 disks of 1.9TB. So, just classic msdos partitions.
> > > One thing is for sure, HP tries really hard to make it complicated...
> >
> > Why would you make 5 logical drives? Why use partition tables?
>
> Hum... just wanted to be fdisk friendly (no gpt)...

The is no reason to be ms-dos-partition friendly on the "data device", IMO.

> But, since grub problem should be solved, I guess I could make 1 big
> logical disk with gpt and forget about fdisk...

Don't mix things up here, fdisk is a tool that can only handle ms-dos 
partition tables. parted is a tool that can handle many types, including gpt. 
It's the partition table type that is the problem not the tool so to speak.

> > I saw that the use of LVM was tossed around, don't know if the OP
> > is/plans on using it. If you use ext3 on lvm, you can do a background
> > fsck while the system is up & fs mounted:
>
> I must admit that I have never used lvm...
> We don't really need resizable/expandable volumes, etc... the server's
> capacity is already maxed. We try to follow the "KISS" principle as much as
> we can.

You can look at LVM as just another way to partition a drive. In that sense 
it's more flexible and harder to mess up than using, say, parted+gpt.

With parted+gpt you'd partition the /dev/cciss/cXdY device into many cXdYpN 
devices. With lvm you'd get to name them and they would be available 
as /dev/VOLUMEGROUPNAME/LOGICALVOLUMENAME.

Go with the way you know and understand.

> But the live background fsck seems nice.

This feature seems to violate the KISS principle for sure...

/Peter

> Do you really think I should learn lvm rightaway?
>
> JD
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