Adding meta to meta LUN will create performance issue.
I'd make a correction here. "Adding meta to meta LUN *can* create a performance issue" It's entirely dependent on how the meta components are laid out. Meta's can also improve performance if done correctly.
There is one very important basic rule to follow with Meta's to avoid most of the performance issues..
NEVER stripe on the same physical disks, only Concatenate when Meta components are sharing disks. Creating a Meta where multiple striped components are sharing the same disks will cause head thrashing and higher response times.
The same rule applies at the host level as well.. Don't allow LVM (VxVM, ASM, etc) striping across multiple LUNs coming from the same RAID Group.
If you have components that are created on separate RAID Groups, then Stripe them. This will improve overall performance of the LUN due to the larger number of disks supporting the meta compared with a single LUN in one RG.
ie: A 200GB striped Meta across 3 x 4+1R5 RAID Groups will perform better than a single 200GB LUN in a single 4+1R5 RAID Group. A 200GB concatenated Meta in a single RAID Group will perform roughly the same as a 100GB normal LUN in the same RAID Group.
If you just need to increase capacity and want to use free space that is in the same RAID Group as the existing LUN, then concatenate.
Of course, if you have the luxury of free space elsewhere in the array where you can create a new larger LUN, a LUN Migration to the new larger LUN would be a good idea.
My understanding and as per document:
A complex metaLUN consists of two or more metaLUN components.
metaLUN = Base LUN + Component LUN(s)
Complext metaLUN= 1st metaLUN + Component LUN of other metaLUN you want to concatenate.
My understanding is you asked, if this is possible:
Complex metaLUN = metaLUN 1(Base+ Comp) + metaLUN2 (Base+Comp), right?
Ankit wrote:Complext metaLUN= 1st metaLUN + Component LUN of other metaLUN you want to concatenate.
AnkitM, How can components LUN of a metaLUN be attached to another MetaLUN.
What I understood about complex meta is where we use both the expansion types,
1 MetaLUN + new components (either striped or concatenated)
Correct me if I am wrong.
True that, I am discussing this with a colleague and will post the response later this evening!
So far what I have read It is mLUN + new Comp. Lun but there are many types in this so I would need some time to post a detailed response!
Vipin V.K, you are right. Component luns of a already created metalun cannot be detached and be used in another metalun. In all the figures wherever you see expansion the base lun is taken into account and the base lun has to be always taken whenever the meta is being done.
Reffer to page 31 of the doc thatAnkitM, mentioned.
Rule : MetaLUN can have one or more metaLUN components. At a minimum, the first component always includes the base lun.
So which means No right?! You can't merge 2 metaLUNs via Expand Option as concat!
You can add a Comp. LUN of another metaLUN to other mLUN not whole metaLUN.
Can I concatenate a MetaLUN with another MetaLUN?
Rupal Rajwar He can concat componenet LUN of other metaLUN after detaching it to the one he wants right?!
If yes, thats what I am trying to explain! 😐