CentOS - Aug 2010 - upgrading storage on hardware RAID 10 possible?

Hi all,

Can anyone please tell me, from experience, if it's possible to
upgrade the hard drives in a RAID 10 system from 250GB HDD's to 500GB
/ 750GB HDD's, while the server is running? The server runs CentOS 5.5
x64.

Our hardware vendors simply always say no, so we never actually tried
doing this, and when a client needed an upgrade like this we had to
build a new server with the same spec and larger hard drives and then
migrate the data across, which can sometimes take a few days to
complete (due to DNS & MAC address caches).

So, I'm wondering, is it possible (and safe) to upgrade the existing
drives to larger drives in a running server?


I know we're done this with Linux's software RAID many times with
great success. But I don't want to take a risk if it's not possible.
The amount of effort and upfront costs for a new server makes hardware
RAID far more expensive than it's reliability, which Linux's software
RAID offers equally so I'm beginning to think we should just move all
the servers to software RAID in the future as well.

-- 
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532

2010/8/13 Rudi Ahlers <Rudi at softdux.com>:
> Hi all,
>
> Can anyone please tell me, from experience, if it's possible to
> upgrade the hard drives in a RAID 10 system from 250GB HDD's to 500GB
> / 750GB HDD's, while the server is running? The server runs CentOS 5.5
> x64.
>
> Our hardware vendors simply always say no, so we never actually tried
> doing this, and when a client needed an upgrade like this we had to
> build a new server with the same spec and larger hard drives and then
> migrate the data across, which can sometimes take a few days to
> complete (due to DNS & MAC address caches).
>
> So, I'm wondering, is it possible (and safe) to upgrade the existing
> drives to larger drives in a running server?
>
>
> I know we're done this with Linux's software RAID many times with
> great success. But I don't want to take a risk if it's not
possible.
> The amount of effort and upfront costs for a new server makes hardware
> RAID far more expensive than it's reliability, which Linux's
software
> RAID offers equally so I'm beginning to think we should just move all
> the servers to software RAID in the future as well.
How about installing new raid 10 on same machine and just migrating
data using rsync ?
after some rsync cycles, just switching to new raid 10 storage.

--
Eero

From: Rudi Ahlers <Rudi at SoftDux.com>
> Can anyone please tell me, from experience, if it's possible  to
> upgrade the hard drives in a RAID 10 system from 250GB HDD's to 500GB
> /  750GB HDD's, while the server is running? The server runs CentOS 
5.5
> x64.
> Our hardware vendors simply always say no, so we never  actually tried
> doing this.
> So, I'm wondering,  is it possible (and safe) to upgrade the existing
> drives to larger drives in  a running server?
When you said "we never  actually tried"... tried what exactly?
It depends... on your RAID ctrl of course...
By example, with HP SmartArrays, you should be able to unplug a disk, plug a 
bigger one and let it rebuild.
Rinse and repeat for all the disks.
Then, you can expand the array...
Although I did not try it so far.

JD

Hi,

Firstly, I would recommend you spend a bit of time and workout RAID  - 
what it means and what it does.

On 08/13/2010 08:50 AM, Rudi Ahlers wrote:
> Can anyone please tell me, from experience, if it's possible to
> upgrade the hard drives in a RAID 10 system from 250GB HDD's to 500GB
> / 750GB HDD's, while the server is running? The server runs CentOS 5.5
> x64.
Yes. But..
> Our hardware vendors simply always say no,
Where it the raid metadata stored ? what kind of an hba is it ? what is 
the volume manager on there ? If you can answer those three questions, 
you can then workout what your options are.

Personally, the safest option is to go with with Ero has already pointed 
out, setup a new Vol, migrate your data.

- KB

On Aug 13, 2010, at 3:50 AM, Rudi Ahlers <Rudi at SoftDux.com> wrote:
> Hi all,
> 
> Can anyone please tell me, from experience, if it's possible to
> upgrade the hard drives in a RAID 10 system from 250GB HDD's to 500GB
> / 750GB HDD's, while the server is running? The server runs CentOS 5.5
> x64.
> 
> Our hardware vendors simply always say no, so we never actually tried
> doing this, and when a client needed an upgrade like this we had to
> build a new server with the same spec and larger hard drives and then
> migrate the data across, which can sometimes take a few days to
> complete (due to DNS & MAC address caches).
> 
> So, I'm wondering, is it possible (and safe) to upgrade the existing
> drives to larger drives in a running server?
> 
> 
> I know we're done this with Linux's software RAID many times with
> great success. But I don't want to take a risk if it's not
possible.
> The amount of effort and upfront costs for a new server makes hardware
> RAID far more expensive than it's reliability, which Linux's
software
> RAID offers equally so I'm beginning to think we should just move all
> the servers to software RAID in the future as well.
If you create a bunch of RAID1s on the HW controller and use LVM to stripe them
into a single VG, you can then pvmove LVs off a RAID1, take it out of the VG,
replace it with a larger RAID1, re-add it to the VG, pvmove the data off the
next one and so on.

This will require you to either keep 50% of the space free for moves, or free
slots open in the disk enclosure. You will also have to manually resilver the
LVs afterward to have them striped properly (create new LVs and copy/move the
data over).

-Ross

> Can anyone please tell me, from experience, if it's possible to
> upgrade the hard drives in a RAID 10 system from 250GB HDD's to 500GB
> / 750GB HDD's, while the server is running? The server runs CentOS 5.5
> x64.
>
(snip)
>
> So, I'm wondering, is it possible (and safe) to upgrade the existing
> drives to larger drives in a running server?
Assuming we're discussing hardware RAID then the answer is *maybe*.
Some raid cards support array expansion through disk replacement and
some don't. Your vendor may be correct in saying the systems doesn't,
they may not. Only way to know for sure is to reviews the spec sheet
of the raid controller you use and look for something along the lines
of "Online Capacity Expansion" (IBM's term for the capability) or
the
like.

I went through this exercise recently with some older IBM server's I
inherited in my department. We wanted to upgrade the disk's in one
server from 36's to 74's and after consulting with my vendor, and my
own digging, it was determined to be impossible. The new controllers
being shipped otoh do come with the capability and I've made a point
of only ordering cards with the feature.


-- 
Drew

"Nothing in life is to be feared. It is only to be understood."
--Marie Curie