Cx3-80 Newbie question : Raid 5

First question i have is this raid group carved on the vault drives?

If on vault drives, usable space from a 6 disk Raid 5 with 73G drives will be 168G.  If that raid group is not carved on the vault drive, you should get 333G worth of space.

I think your raid group is actually 5 disk raid 5 on the vault drives.  the useable space for that config is 134G and your 2 lun's are consuming that space.

For your second question,  it depends on which lun you unbind first.  look at the properties of the raid group on the partition tab and you can see which lun is first in the group.  if you remove the first, you will have space available before the second lun.  but since you dont have any extra free space in that raid group, you wont get any added space by defraging

if you have 200GB of free space in two equally large areas of 100GB each and you only need to create 1 or 2 100GB LUN's you don't have to defrag at all !

Furthermore: if you have a 100GB "gap" on the left and a 100GB LUN on the right, you could also trigger a LUN migration of that single LUN. This way not all LUN's of that RG will be moved, just that one.

And finally: I wouldn't want to defrag just because you can. The design may be that certain LUN's have to be on the edges of the RG, to keep busy LUN's together in the middle.

The best way to allocate LUN's in a RG for performance reasons is as follows: put the busiest LUN's in the middle and the further you go to the edges, the lower the performance of those LUN's have to be. This way the hard drive's heads will mostly be active in the middle of each disk and therefore perform better !

To Kenn2347

That is the case I have bus 0 enclosure 0  disk 0 to 4.

http://clariionblogs.blogspot.com/2008/01/vault-drives.html

I understand  everything you said.

To Allen Ward:

Is it good idea to defrag imeddiately?

Ok,  what I want is to get some disk space free. There is a RAID Group consisting  of 8 LUNs,  3 out of them appaers to be non allocated to any host. There is no any private LUN in the group. These numbers are  3, 4 and 7. Partitioning follows the order of numbers  (First Lun1, Lun2....Lun8).

LUN properties, host tab – no host information, nor Physical Device name neither Logical Device name. So, that means that  particular LUN is not  connected (allocated) to a host(server)?

However, the help is a bit confusing:

There is no the above text, and I am confusing. Neither host information  nor LUN Drive mapping for host appear dimmed, but they are empty.

Can I unbind these LUNs, defrag raid group  and bind to it  LUN 3 times capacity of the identical LUN inside the raid group?

LUN migration is used to move a single (or more than 1) LUN('s) to the same or a different Raid Group in order to:

- change a storage tier (move from SATA to FC or vice versa)

- move from a METALUN to a single LUN or vise versa

- clean up a Raid Group instead of having to defrag the whole Raid Group (this only works if there's a LUN at the end of a RG equally sized as the "gap"  somewhere in front or the middle

How do you perform this LUN Migration ?

Create a new LUN in the area where you want to have the LUN migrating to. If you have a 100GB in the beginning of a RG and you want to move a 100GB LUN that's in the back, create a 100GB LUN with any LUN address. Now right click on the LUN you want to move and choose "migrate". Now choose the newly created LUN and voila: the migration will move the data from your original LUN to the new location and in the end the new LUN takes the identity of the old LUN. And the best part is that it's non disruptive !

Do not know what do you mean by trigger migration?

Do not forget pools.

LUN migration will move you in and out of pools, and through proper technique can be used to create a move favorable layout of storage within the pool.

@ RRR

I wasn't considering a special performance consideration for LUNs on a RAID Group. I was answering more from the perspective of the question being asked from someone looking at a basic configuration. You are right though that I should have qualified it so others reading it later would realize that this isn't ALWAYS the right thing to do.

@DoleBlogger

As per the comments from RRR, this isn't ALWAYS the right thing to do, but if you are not configuring your LUNs for special performance based on RAID Group layout then it makes more sense to defrag sooner than later. I can't count the number of times I've tried to provision a LUN for an "emergency" situation and then needed to wait for a defrag to complete before I could get the LUN I needed.

so true

when you say "middle of the RG" does that mean "middle of the disk"?  i have heard of the positioning on the disk, never on the RG level.

Since the disks are striped both means/do the same thing. Just want to verify.

If you right-click on the Raid Group icon and select Properties, then select the Partition tab. This will show you the layout of the LUNs in the Raid Group. If LUNs 3, 4 and 7 are not being used by any host, you can unbind the LUNs, then defrag the raid group. That will more LUNs 5, 6 and 8 next to LUNs 1 and 2, leaving the rest as free, contiguous space. You can then create a new LUN using all this empty space.

As to the LUN Properties\Host tab - if the LUNs are not assigned, you can unbind, if the LUNs are being used, it will not allow you to unbind. LUN's that are Private or assigned to host will not allow you to accidently unbind.

glen

Side note on this:  Do not use 0/0/0 - 0/0/4 for Raid Groups.  This can and will come back to bite you later. For example:

1. It can cause you not to have enough space for FLARE code upgrades to major releases.
2. It can possibly restrict in place upgrades to different array versions.
3. Can cause issues with FLARE or Vault activity due to unexpected high I/O on the drives.

Generally, just don't do it if you can help it at all.

TJ

Thanks very much. It has been answered. Above all, it works

Tkjoffs,

Thanks, I see what you mean. The people who installed the system  before,  made wrong set up. I will have to correct it.