Adding new disks to ME4084

Hello DB_2022,

You are correct. Page 64: The drawers must be populated with DDICs in whole rows. Each drawer contains 3 rows of 14 DDICs.  : https://dell.to/3Y4ME7a

You would need to fill a full row, 14 DDIC, at a time. So if you add 14 DDIC to the bottom drawer then the next time you will add 14 DDIC to the top drawer. The number of populated rows should not differ by more than one row between the top and bottom drawers.

The reason why two minutes is mentioned is because the normal airflow is disrupted when you have a drawer open.  If you have it open to long then components can get to hot.

In normal circumstances, after closing the drawer, everything should be back to normal temperature within a few minutes or listen for the fans to return to normal speed.

Charles,

Thanks for the reply. Does populating in whole rows mean you have to put 14 disks in at one time (i.e. within the two minutes), or can I put 7 in, shut the drawer, let it normalize, open the drawer and put the other 7 in so I have 14 in the row?

Is the two minutes a hard limit or is it just a "recommended due to airflow issues" limit? i.e. if I was to have the drawer open for 2 minutes and 5 seconds, would the system start shutting things down/having problems?

Thanks.

Hi @DB_2022,

The recommended installation is 14 in 1 row at the same time, but it did not state if it's not possible to install 7 twice. We may need to check on this, might get back to you. 

The 2 minutes is not a hard limit. It is the recommended procedure time duration, for temperature to sustain. Once the temperature gets too warm for the storage, the system will shutdown. 

Are you sure the ONLY reason for the two minutes is temperature? For example, does pulling out a drawer disconnect that drawer's drives from the system (temporarily) and so the two minutes is also due to an I/O cache limit or something like that?

Yes, please check on it for me. If there's documentation you can post/screenshot, even better.

Thanks.

Hello DB_2022,

Opening the drawer does not disconnect the drives. The drives are hot swappable:

Replacing a drive carrier module in a 2U enclosure

https://dell.to/3WQG2rX

The manual says install complete rows (14) at a time so I could not advise against that, like doing fewer drives.

Page 64: The drawers must be populated with DDICs in whole rows. Each drawer contains 3 rows of 14 DDICs.  : https://dell.to/3wInIqu

Hello DB_2022,

It is documented:  The drawers must be populated with DDICs in whole rows

I did speak with a Storage engineer and was advised:

Well the guide says they must be added to slots in complete rows of 14 at a time so I personally wouldn't do just 7.  Air flow would be a little uneven and the drives on the side with more may get warmer than the other side.  I would try to stick to the guide and just insert all 14 drives to fill the whole row at once.

I can only advise what the documentation says.

Okay, thank you. Is it documented anywhere that the reason for the two minutes is for airflow considerations? The guides just say "only two minutes" and don't say why, or what happens if you go over the two minutes.

Installing "in complete rows" doesn't have to mean "install all 14 within two minutes". It could just mean "make sure a row is full before you put disks in a different row". I've seen several people on this community who have stated they have less than a multiple of 14 drives (e.g. 20, or "we have 4 slots left") installed in their system. This would indicate that the system can handle having less than 14 in a row, as long as only the last row in the sequence has less than 14 (e.g. fill row 1 in the top drawer and row 1 in the bottom drawer, and then if you put less than 14 in row 2 in the top drawer that's okay, but you can't have a full row 1 in the top, 7 in the row 1 in the bottom, and 7 in the row 2 at the top).

If you don't know for certain, can you find out for us?

Thanks.

Thanks, but I don't think you caught what I was trying to ask earlier. I realize that the final state of the system should be 14 disks in each row. But installing 14 disks in under two minutes is a little over 8 seconds per disk, which isn't all that long, especially if one gets stuck or there's some other hiccup in the process. I'm just asking if you can install 7, shut the drawer, wait for it to settle, open the drawer again, and install the other 7. So all 14 would be installed within a few minutes of each other, just in two goes rather than one. The system's still being installed in "whole rows", just broken up by the closing and opening of the drawer halfway through.

Can you check with your storage engineer if this is okay?

Also would you kindly check with your engineer whether or not there's an indicator on the system telling the user when it's safe to open the drawer again after opening and closing it? If there isn't one, how long is it recommended to wait before opening the drawer again?

Thanks.

Also, is it documented anywhere that the reason for the two minutes is for airflow considerations? The guides just say "only two minutes" and don't say why, or what happens if you go over the two minutes.

Hello DB_2022,

Some people that have less than multiples of 14 are not following best practice. If you don’t fill the whole row then airflow is going to take the path of least resistance where you left gaps. Drives that are getting less airflow could be getting warmer than they would be otherwise. Prolonged high temperatures will probably decrease the lifespan of a hard drive.   Read the hot surface label affixed to the drawer. Operating temperatures inside enclosure drawers can reach 60ºC. Take care when opening drawers and removing DDICs.

Documentation for the two minutes and reason are shown here:

"drawers must not be left open for longer than two minutes, or airflow and cooling will be compromised"

Page 20 here : https://dell.to/40ffnrD

Each disk drive is shipped with a new disk drive in carrier (DDIC). Install the disk drive in the DDIC before opening the drawer. If you have them all prepared before opening the drawer then installation should go rapidly.

Remove a DDIC only if a replacement DDIC is available.

NOTE: Closing a drawer with one or more DDICs missing can potentially cause cooling problems. See Populating drawers on page 64.

There is not an indicator specifically for when it is ok to open the drawer again.  After closing the drawer, everything should be back to normal temperature within a few minutes or listen for the fans to return to normal speed.

If there is a high or over temperature alert this will show in the MESM management interface and the ops panel on the front of the device will have a warning light to indicate in there is some sort of fault in general.

My advice is have all the DDIC's assembled, install the 14 drives and then close the drawer. As long as you're staying on task and doing it in a reasonable amount of time it should be fine.

Charles, thanks for your patience with my responses. Your replies have been very helpful.

I was most concerned about the ME4084 shutting down or something equally production-impacting if I went over the 2 minutes. Now it sounds like it's not an issue if I'm a few seconds over (but of course I will endeavor to remain under 2 minutes).

Thanks again.