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We have inherited responsibility for a Dell Equallogic PS4000 SAN that was configured with a single default pool and a single RAID 5 member that was using all 8 disks.

Having now added 8 additional hard drives the existing member has absorbed the new hard drives and the member is stuck at RAID5 (as documented). Ideally I would like to set the whole thing up as RAID50 but I have a feeling there's no way of doing that without having to move all the data off to something else and then back on.

Member utilisation is 4.04TB (1.13TB reserved, 7.05TB free). Currently the member contains 3 volumes, each of which is presented to two (about to be three) ESXi 4.1 hosts.

Is there any way to shrink the member in order to create a new member in the reclaimed space?

Following my previous question I will also attempt to obtain an answer through Equallogic support and report back here on their answer...

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up vote 5 down vote accepted

it’s Joe with Dell EqualLogic.

The EqualLogic arrays utilize all available disk space on the member for the RAID set. So, you can only have one RAID policy per member. There is no way to shrink the size of the RAID set, and create another RAID set on a single member.

You have two options;

1: As you surmised, since this is a single member group, you would need to remove the data from the array, than remove the member from the group. But, since this is a single member group, when you remove the member, you would in fact, destroy the entire group (all volumes, settings, IP’s, SMTP, SNMP, ACL’s etc.).

When removing a member from a single member group, you would first need to capture all the group information.

Once the member is deleted from the group, when you recreate the group (and the member with the RAID-50 policy), you would need to re-input all the settings.

You can do this manually, or use the "save-config" command prior to destroying the group: The save-config command can be run in default or group-only mode.

In default mode, the resulting file will automatically restore the following:

  • Replication partner configuration
  • Storage pools
  • Member RAID level, pool, and network interface configuration
  • Group customization, including lists of servers
  • Volume configuration, including access control records
  • Volume collection configuration
  • Schedules for snapshots and replication
  • Local CHAP account configuration
  • Event settings
  • Account configuration

If you specify the save-config command with the -grouponly parameter, member and pool configuration information will be saved as comments instead of commands, so you must manually restore these parts of the configuration. A member’s RAID level and pool must be selected before you can use the storage.

The save-config command will not restore the basic member network configuration or the group configuration, but it will save this information as comments in the restoration file. The following information must be manually supplied to each member by running the setup utility:

  • Group name and IP address
  • Passwords
  • Member name, IP address, default gateway, and netmask

2: The second option requires a second EqualLogic array (contact you sales person to see if they have a loaner you can borrow).

If you have a second array, you would first create a second storage pool in the group (initially it would contain no members). Once the pool is created, you would then initialize the second array AND add this array to that new pool.

Once the new member is added, move the volumes from the existing member (in the default pool) to the new member (this will take some time depending on the amount of data, network, etc., note that this can be done while the array is serving up data, so there is no downtime during this process).

Once all the volumes are vacated from the original member, you can then remove the original member from the group (delete member), and reconfigure it to RAID-50, and add it back into the group in the same pool it was removed from (do not add it to the pool with the loaner/spare member).

Once the original member is back in the original pool, you can then move the data from the 2nd array back to the original member (again, this can be done without downtime).

Once the data is moved back to the original member, you can remove the loaner/spare member.

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Awesome answer thanks Joe... 'There is no way to shrink the size of the RAID set, and create another RAID set on a single member.' I fundamentally misunderstood what a "member" is... I assumed you could have multiple members in a single unit/enclosure (a bit like you can have multiple disk groups on an EVA). I now know member=unit. Thanks for the clear and accurate answer, it far exceeded the response I got through the official support channel! :) –  Matthew Sep 28 '11 at 22:54
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