Re: Upgrade raid0 to raid1

On 23 Lis, 22:41, General Schvantzkoph <schvantzk...@xxxxxxxxx> wrote:
On Fri, 23 Nov 2007 13:13:38 -0800, Kedarius wrote:
Hi,
I would like to ask, whether there are any possibilites how to upgrade
running raid0 to raid1.
I have two 2GB flash drives running as raid0 and I would like to change
it to two 4GB flash drives running RAID1 without stopping the array. Is
this somewhat possible?

Radek

Plug in the other two drives, configure them as RAID1 and then copy the
contents of the old drives to the new ones.

RAID0 and RAID1 perform two separate functions, RAID0, otherwise know as
striping, increase your bandwidth. RAID1, otherwise known as mirroring,
replicates the data on two drives to provide redundancy. If you have more
that two drives then you can combine the two functions in a RAID5 array.
However with just two drives your choices are 0 or 1 and they are not
compatible. If you pull one drive on a RAID1 and replace it with another
then you can rebuild the RAID set. If you pull one drive from a RAID0 you
have nothing be cause the data is spread across both drives.

Just curious, why are you doing RAID with FLASH drives? FLASH drives are
great for moving data around but I'm not sure I would want to use them as
my main storage. FLASH drives have very slow write times, and they also
have a limited number of write cycles. In cameras, phones and MP3 players
this doesn't matter because they are fast enough and you do very few
writes to any particular location. I'm assuming you are using them for
some very low power application, but I would think that a single drive
would be best for that.

I know that I can move data by copying files. And I think this will be
the only one option but I was curious whether there is some
possibility doing this without stopping the RAID. Some magic with raid
upgrading (i.e. to raid10, etc :-)
We are using flash drives as / partitions for some of our servers. The
data and /var partitions are mounted from iSCSI drive. We've also
tested speed of these drives and we were able to achieve 15-20MB/s for
sequential write and read. The main reason for this is that we have a
lot of same hardware in custom made blade cases and two iSCSI servers
with a lot of capacity. The blades does not need HDD (in fact they are
only motherboards and PSU on a metal plate :-). We can easily move/
duplicate/etc. the flash images and the actual systems are independent
on the hardware. Deployng new server means copying prepared flash
image to new flash drives, changing hostname, IP, root pasword and
booting on new HW.
We use flash drives in raid1 so we can replace one in case of failure
or when flash drives reaches its maximum writes count. Unfortunatelly
in this one case customer insisted on buying two 2GB drives and
striping them because 4GB drives were much more expensive than two 2GB
then. And the server was experimental so downtime was no problem. And
of course the server has moved from experimental to production since
and now he would like to avoid downtime. And I was curious if this is
possible....
Next step would be mirroring flash drives to iSCSI server and maybe
removing flash drives completely but for now we are rather happy with
this solution. And customers too, becasue they buy for example 2x500GB
HDD and can share it between 5 servers each with 100GB mirrored disk
capacity.
.