Expanding LUNS on Oracle DB server

Question

Hi

I need to know some recommendations on expanding LUNS on oracle DB servers ¿ CX700 SAN (or in general on DB servers).

Can there be any performance issues depending on expansion method I use (Concatenated vs. striped). LUNS in question is on RAID 10 and it has to be maintained in RAID 10 and current size is 50GB.

It¿s required to expand this 50GB LUN up to 200GB.

Is it recommended to add chunks from the same raid group or split it across different raid groups? Or is that depend on which expansion method I use (concatenated or striped)

Thanks in advance

Kiran3 · Accepted Answer

Is it recommended to add chunks from the same raid group

No.using meta luns from same RG will cause longer disk seeks because all luns will use same physical disks and this will cause non-optimum i/o performance.

Can there be any performance issues depending on expansion method I use

if you use striped expansion, there can be performance issues when the lun is being expanded.
while striped expansion, source and target luns need to be same size and same raid type...in your case you will have to expand the lun with a 50GB lun first and then with a 100gb lun.
with concatenation, luns can be of varying size and type (not recommended). so you can directly use a 150gb lun to expand your 50gb.

you can perform the expansion in two ways...either you can add unbound disks to the RAID group and then expand the lun on same raid group (striped expansion here). even though i said no to use luns from same RG, you can do it here since you are adding disks.

or you can use free space from another raid group to expand your lun (preferably concatenation). this again adds more disks spindles and distribution of i/o on them..and gives a better performance.

Kiran3 · Answer

.

an_hidden_KB · Answer

in short - if you're looking for performance, you do not want to use concatenated metas nor put the meta components on the same raid group. worst you could do is put striped meta members in same group, that will make the drives seek like hell.
there's lots of good information about configuring clariion (including metaluns) on whitepapers available on powerlink

T23 · Answer

Hi Guys

Thanks so much for the useful information.

Could you please answer this? What if, I do a striped expansion with LUN in different raid Group (Same raid type and size)? Is it recommended for striped expansion?

What impact will this have on IO, if it¿s on the same BUS.? Could you point out the best scenario to follow, I believe its scenario 02.

For example

Raid Group 0 = Bus 0, Disk 0, 1, 2 ==>Lun100
Raid Group 1 = Bus 0, Disk 3, 4, 5 ==>Lun101

Raid Group 2 = Bus 1, Disk 0, 1, 2 ==>Lun102

Scenario 01 ==> expanding LUN 100 with LUN 101 on striped

Scenario 02 ==> expanding LUN 100 with LUN 102 on striped

Regards

an_hidden_KB · Answer

Could you please answer this? What if, I do a striped
expansion with LUN in different raid Group (Same raid
type and size)? Is it recommended for striped
expansion?

yes, perfect

What impact will this have on IO, if it¿s on the same
BUS.? Could you point out the best scenario to

this difference is not significant, but is does not hurt either to utilize different busses

Message was edited by:
Ain Pariis

an_hidden_KB · Answer

while striped expansion, source and target luns need
to be same size and same raid type...in your case you
will have to expand the lun with a 50GB lun first and
then with a 100gb lun.

i need to correct this: when striping, you can expand only to original component sized luns, 50g here. you can have up to 32 component luns per meta and you can add them all in 1 step or add stripe members 1 by 1.

Kiran3 · Answer

oh...didnt know that...I believed that once the lun is expanded to 100GB by adding one 50GB, it behaved like 100GB which I can expand by adding 100GB more..thanks for the correction.

T23 · Answer

Hi Guys Thanks for the feedback. It¿s great. My question is answered. RegardsDharshana

Fernando1970 · Answer

Why do you want to concatenate or stripe to expand a LUN.
Why dont you use the LUN migration process to convert your 50GB to a 200GB disk? It last hours but it toally transparent to the host and user. It doesnt impact in performance.

I always assign a new disk to the host and add it to the VG if LVM on a unix server or create a dynamic volume if a windows.

But if not possible then migrate the LUN and extend the LV and filesystem or expand the disk with diskpart in microsoft OS.

Hope it helps you.

Best regards.

CLARiiON

Expanding LUNS on Oracle DB server

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