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Best order to add disk drives to EVA 5000?

Alan Striegel_2
Occasional Visitor

Best order to add disk drives to EVA 5000?

One of our services specialists in the field asked this question and I couldn't find anything definitive. Any help?

Alan

"I am on currenlty on a customer's site working with an EVA 5K and have run into the following dilema:

An HP engineer has stated that disk drive placement on the EVA should begin at the left and move toward the right (to attain proper drive numbering in Command View). He stated that the reason the drives ship in the middle is for load distribution when shipping.

My thought process was that the drives were shipped in the middle (of the disk shelf) to balance disks across all fiber loops.

If anyone has a correct answer, or can point me to HP documentation that states correct drive placement procedures it would be very appreciated. I do not want the customer to end up in a sub optimal configuration. -- and if I am wrong I would like to be corrected. Note: I have reviewed "almost" all information on HP's website."
3 REPLIES
Alan Striegel_2
Occasional Visitor

Re: Best order to add disk drives to EVA 5000?

In answer to him, I sent the following:

I haven't seen this exact issue addressed directly by anything from HP, but there is a guideline in the EVA Best Practices document (ftp://ftp.compaq.com/pub/products/storageworks/whitepapers/EVA_Best_Practices_White_Paper.pdf) for availability that states you should pay more attention to the disk subgroups. The relevant section is quoted below:


In order to protect against loss of data access in the event of a shelf failure, there must be no more than one disk in a specific redundancy set per shelf. This requires a minimal amount of effort by the user at the time the disk group is created. The steps taken to accomplish this vary, depending on whether a LUN is configured as VRaid 1 or VRaid 5. If a mixture of VRaid 1 and VRaid 5 are contemplated for a single disk group, then the guidelines for VRaid 5 should be followed. If only VRaid 1 will be used, then the VRaid 1 guidelines are appropriate.
VRaid 5 availability best practice:
1. There should be a minimum of 8 shelves in a configuration for VRaid 5.
2. All disks should be arranged in a vertical fashion, i.e., distribute the disks among the shelves such that the same bay in each shelf has a disk.
3. The total number of disks in a disk group should be an integer multiple of eight.
4. When creating a disk group, let the EVA choose which disks to place in the group.
With VRaid 1, the EVA firmware will attempt to place the individual members of a mirror pair on different shelves. Because of this, the guidelines are much simpler, and there does not have to be a minimum of 8 shelves.
VRaid 1 availability best practice:
1. All disks should be arranged in a vertical fashion, i.e., distribute the disks among the shelves such that the same bay in each shelf has a disk.
2. When creating a disk group, let the EVA choose which disks to place in the group.
Alan Striegel_2
Occasional Visitor

Re: Best order to add disk drives to EVA 5000?

In addition, I sent the next message:

To add to what I sent earlier, there is no choice among loops by placement within the shelf. Every disk in a shelf is on both the A and B loops. According to the document, "hp StorageWorks Adding M5314 Drive Enclosures to an EVA5000 Configuration" (http://h20000.www2.hp.com/bizsupport/CoreRedirect.jsp?targetPage=http%3A%2F%2Fh200007.www2.hp.com%2Fbc%2Fdocs%2Fsupport%2FSupportManual%2Fc00062123%2Fc00062123.pdf):

The location of the drive enclosure in the rack determines to which loop switches it connects. Drive enclosures mounted in the lower half of the rack (enclosures 1 through 6) connect to loop 1A and 1B. Drive enclosures mounted in the upper half of the rack (enclosures 9 through 14) connect to loop 2A and 2B.
Uwe Zessin
Honored Contributor

Re: Best order to add disk drives to EVA 5000?

Alan,
I have not seen any arguments how to 'properly' fill the disk drive enclosures either. We always fill from left to right. I have placed a disk in an enclosure with free bays on the left and right side. CommandView EVA displays it properly and I even see that there is room in the AL_PA space for the empty bays between the disks. That is not really important, because the user need not be concerned with the AL_PA of a disk drive.

All bays in one disk enclosure are connected to the same pair of fibre channel loops - there is no 'balancing'. You can only balance entire enclosures between the loop pairs 1+2 on the EVA-5000. It makes sense to equally distribute the disks over all enclosures, but you know that already.
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