EVA8000 swaping 300GB with 600GB disks

[Louis Henninger_1]

We are upgrading firmware from XCS6.0 to XCS6.22 (HP upgrading). During this outage we want to replace 24 of 44 ungrouped disks with 600GB FC 15K disks. They are currently 300GB FC 10K disks. I have mapped out all of the ungrouped disks, but rather than trying to follow best practices manually, I was thinking of creating a new disk group of 24 disks. Once created, use locate feature to find all disks the EVA "selected" as best possible disks (RSS etc.) Prior to shutting down the EVA for the firmware upgrade, dissolve the disk group and replace the 30GB disks with 600GB disks.Or would it be better to leave the created disk group and ungroup each 300 disk, replace with a 600GB and regroup one at a time?
I want to end up with a disk group of 24 disks of 600GB each. I'm thinking the disk, being 15K will still work without any problems even though the rest of the disks on eth shelves are 10K. Anything I'm missing?

Thanks,

Louis

[Peter Mattei]

Hi

Why doing it so complicated?

If the disks have already been ungrouped, just pull them one by one.

If you have less than 8 diskenclosures just install your 24 disks and build your disk group.

If you have 8 or more enclosures, insert 8 disks vertically and build your disk group.
Then install the next 8 disks and add them to the group.
Then install the last 8 disks and add them to the group.

Notes:
1) When insering disks into a disk enclosure - always wait 1 minute after you have installed a disk before you plug the next one
2) I would do these actions AFTER the XCS upgrade. It is usually best to do that with the latest firmware. Dont forget to check the disk firmware after the disks have been installed!

Cheers
Pete

[Louis Henninger_1]

Peter, Thanks for reply. I have a 2c12D + 0C6D configuration with 240 disks. I can spread out the disks myself, but thought the HSV210-A could do a better job of selecting disks for the new group. If I installed the 600 GB disks into the EVA, would the controller pick all 24 of the 600GB disks automatically?

Louis

[Peter Mattei]

The EVA will recognis the new drives automatically and put them in the Ungrouped Disks older.

If you then create a new disk group with 24 disks the EVA will try to build an optimal layout.
If you create the disk group with 8 disk first these will build an RSS set.
Adding the second 8 disks will most probably add the second RSS and so on.
Performance wise both ways will be equally because the EVA will stripe all data across all drives in a disk group with restriping when adding disks

Pete

[Louis Henninger_1]

Peter,

Would the controller know which disks I wanted to create a disk group with? I mean, I have 44 ungrouped disks, consisting of twenty 300GB disks and 24 (new) 600GB disks.

If I wanted to create a group of 20 disks, would the eva ask which type I wanted?

Louis

[jason andrade]

New to EVAs but from my experience louis, the EVA seems to pick the 'first available' rather than any sort of choice offered to you. i haven't quite worked out the algorithm it uses to pick though (e.g smallest disks first?)

so if you want to build a disk group of 24 600G disks, first build/use up the existing disks, then remove all the ungrouped disks you don't want. then put in the 600G disks and build your disk group.

this approach has worked for me when building with multiple different sized drives.

[Peter Mattei]

Jason is right
Unfortunately you cannot choose which drives to take for a new disk group.
Afterwards you can add disks individually to a group.

So as Jason suggested I would pull all the ungrouped disks you do not want to group, leave the 20 600GB disks and create the disk group.

Cheers
Pete

[Louis Henninger_1]

If you look at my original post. I was going to create a disk group with 24 disks.

Ungroup and replace eace one with a larger disk...effectivly having EVA choose optimum disks placement (RSS), then replaceing them after creation...

Isn't that what was suggested (Jason or Peter)? Or am I still missing something?

Louis

[Peter Mattei]

Well, reading your initial post I got the impression that you have 44 ungrouped inserted 300GB disk.
You want to replace 24 of them by 600GB disks.
If you now create a new 24 disk disk group you cannot decide which ones will be taken.

Therefore I recommend to remove all ungrouped disks thet shhall NOT be grouped and just leav the 24 600GB disks ungrouped.

Now when creating the new group with 24 disks you will be sure that it will be the 600GB ones.

Cheers
Pete

[jason andrade]

Hi Louis,

What peter said basically.

I am really not sure why you are focusing so much on the RSS sets because really the EVA should work this all out itself, over time and unless you are already really pushing the EVA performance you should have the time and headroom to let it sort it out itself.

Going back to the original question, i read it like this:

44 ungrouped 300G disks.
remove 24 of them
group the remaining 20 300G disks into an existing DG
add in 24 600G disks
create a new disk group with all the 600G disks.

you haven't really said why you are creating a separate group for the 600G disks. over here, we mix different sized disks in the same group (and we are aware of the issues around this but it works for us just fine).

one of the HP thoughts was that (assuming all the other caveats specific to your requirements) mixing disk types
in a disk group is better than different groups of different sized disks IF you were trying to optimize capacity - you also overall got better performance as you were striping across more spindles overall.

our experience on the EVA is we now try to aim for 2 disk groups at most (of FC) with 1 disk group (if FATA on the same array).

regards,

-jason