EVA 5000 adding mix capacity drives

[Joseph Salzer_4]

Hello all.

I have just upgraded a customer's EVA 5k (added 4 disk enclosures). This customer had 8 existing enclosures full with 72GB disks.

The new closures will have 4 x 146GB disks each.

The customer was told by HP that the disks needed to be added one at a time after the enclosure had been installed.

I knew that when you are adding disks to an existing enclosure you add them one at a time and wait around 60 seconds before installing the next disk to avoid to many FC_AL loop signal changes.

All the previous upgrades I have done I have added the disks to the enclosures before applying power to the enclosure and before connecting the FC cables to the switches. Every document I have read doesn't tell me to do any different.

Any feedback on this would be appreciated. I am not saying the HP engineer is wrong, but I am just looking for clarification on this so I can better explain it to our customer.

Thanks.

[Joseph Salzer_4]

One more thing I should add. There is only one Disk Group and Device Addition is set to "Automatic"

Thanks

[Steven Clementi]

When I perform EVA upgrades, I always try to get a maintanence window so I can shut the EVA down. Most of the time I do.

That said, I believe you can add shelves on the fly, but you do need to consider the impact of adding an addition device to a fibre LOOP.

Whether it is a shelf of a disk, you should add only one at a time, wait about a minue then add the next device and so on and so forth, mainly as a precausion. If you add 10 devices at once, and only one of them causes a problem, you can have a major disruption. This is not to say you CAN'T have a major disruption when only adding one device.

General HP Best Practice dictates that you add new devices one at a time. This Best Practice doc is not generally available to the public either. Usually only Certified HP Trained indivuduals will have access to it (nd even then it is sometimes hard to obtain).

Long story short.. the HP engineer is correct, according to HP.

Can you add a whole shelf without any problems? Sure, you've done it before. Is it the bet thing to do? Probably not.

As for mixed capacity drives, sure you can add to an existing group. The impact is this...

1. Your protection level is NOW SINGLE or DOUBLE based on the HIGHER disk size. If you at double... you lose 146GB*4.
2. Your leveling will t ake a bit longer and your larger drives will have about double the amount of data on them vs. the 72GB drives.

Additionally, I would disable the auto add, get all the disks inplace and then add them all at the same time. The EVA will have an easier time figuring out the RSS if you supply it additional drives in multiples of 8.


Steven

[Joseph Salzer_4]

Steven,

I have re-read the best practices doc and this is what it says:

"When adding disks to expand storage system:

.....

* If you are planning on needing to add diks often, try to add disks all at one time. This increases the RSS efficiency."

Further down on a separate section it says:

"Use off peak time to physically add devices to the storage system:

...
* Wait at least 60 seconds between each drive insertion. This allows VCS recognition and reduces FC-AL loop signal changes."

Just to be sure I even consulted the latest pdf on adding enclosures to an EV5000 configuration. It says to do what I have always done, in step 10.

"
...

10. Insert and seat all drives into the drive enclosure."

This is done before even connecting the enclosure to the EAB or loop switches.

Any thoughts on this?

Thanks

[Steven Clementi]

Assuming you were adding a new shelf, you can add the shelf with drives in it and have no problems with Loop singal since the drives and the shelf are all powered up and the drives are already spinning. The 60 seconds is... time to power and spin up as well as time to add itself to the loop and for CV to see it.

If you already have the shelf installed, then yes, you should add disks one at a time to allow for Loop signal, power, spinup, etc.

When I perform upgrades, I like to get the shelves in first, to make sure there are no problems with the ID, or with the loop or with the EMU. Once I confirm the shelf is "ok", I then proceed with the drives. It is, for me, more of a precautionary measure then a best practice.

Steven

[Uwe Zessin]

One comment is talking about physically plugging disk drives into a disk drive enclosure (with automatic addition to the disk group best turned off). Comments that mention RSS talk about adding already recognized disk drives to an existing disk group.

I would not add lots of disk drives to a power-off EVA. If these drives somehow have data from another configuration on it there is a chance greater zero that the system does not start.

[Steven Clementi]

I would not add disks to a powered off initialized EVA at all. I would only add shelves. Power the whole thing on, then add the disks after I verified the shelves were operational.


Steven

[Joseph Salzer_4]

I agree, once I have initialized and EVA I have never really seen a need to have the EVA completely off. Frankly, that is why customer's pay a lot of money for these devices, to have the least amount of downtime. I have always upgraded (ie, added shelves) to live EVAs without any problems. (knocking on wood). I do agree that downtime needs to be scheduled just in case things don't go as planned.

[Uwe Zessin]

I am afraid that is easier said than done. English is not my mother's language, so correct me if I'm wrong, but I think you have to power-down when the EVA does not have loop switches:
Adding M5314 Drive Enclosures to an EVA5000 Configuration
Instructions
Third Edition (May 2004)
Part Number: EK-DEIRE-AA. C01

""This guide tells you how to add an M53141 drive enclosure to an existing EVA5000 rack with FC loop switches, while the EVA5000 is running and in production. You can add M5314 drive enclosures to EVA3000 and EVA5000 racks without FC loop switches while the storage system is shut down.""

[Steven Clementi]

Though I have never hot added a 5314 to a running EVA without Loop switches, I HAVE added an EXP700 to a FastT900 while it was in production. The FastT has not loop switches and is wired like the older EVA... shelf to shelf to shelf to controller.

As long as you do not disrupt BOTH loops on a set, you should be able to hot add a shelf by first disconnecting loop A and putting the new shelf inline. Wait a few minutes to make sure the EVA "see's" it, then perform the same on Loop B.

Again, I have never done it on the EVA and I always suggest downtime for such things.


Steven