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Questions about groups and pools
I'm new to the EQL stuff so I'm still trying to understand how the groups and pools work. Before I go into production with the arrays I want to be sure I understand how things work so I can provision them correctly for my needs and not back myself into a corner.
Below is a summary and some questions of my current understanding of things. Would someone be able to tell me if I'm understanding things correctly?
1) An array must be a member of a group.
2) An array can only be a member of 1 group.
3) An array (lets assume standalone) must be reset and lose all it's data before it can join another group.
4) A group with two members can have one of it's members removed. Upon removal I can choose whether to migrate all luns to the other member or not and the member which is removed ends up being reset, losing all it's data.
a) Am I forced to migrate luns or can I choose?
b) If I use storage vmotion to move things around myself or manually move other types of data myself, I can unpresent the luns, remove the member array, and that removed member will destroy all the data and reset itself, ready to join another group.
5) I was told by the person at Dell helping with this purchase that it wasn't advisable to mix a disk array and a hybrid array in the same pool because it might not distribute data optimally between arrays. Assuming this is correct....
a) Is there any issue if I put these two arrays in the same group but in different pools? Will that keep them "isolated"?
b) Assuming I can do what I mentioned in a) above, can I move luns between pools?
c) If I can move luns between pools, can it be done transparently (ie. zero downtime, no resetting of arrays, vmware won't even know it happened, etc). If I can move and it is transparent, would that work for luns presented to windows boxes or hyper-v as well?
d) If I want to remove a member, and assuming each member is in a different pool, will the EQL automatically move the data to the other array or does that only works for arrays in the same pool?
6) In a 2 member pool with seevral luns presented to vmware, is there any advantage to setting up a storage cluster in vmware and letting vmware recommend whether or not to move vms around or does the EQL shuffle data around between members thereby skewing the numbers from vmware's perspective?
a) If I only have 1 member in a pool and have multiple luns presented in vmware, would I benefit from the storage cluster?
Thanks
Anonymous
5 Practitioner
5 Practitioner
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274.2K Posts
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February 19th, 2014 08:00
There are some tutorials on youtube also but the basic rules are:
1.) The "Group" is the top level abstraction, the starting point.
2.) Groups are comprised of up to 16 "member" arrays.
3.) A member is a single physical unit of storage.
4.) A single member can have from 16 to 48 drives depending on model.
5.) A group can have up to four "pools"
6.) A member array can only be in one pool at a time.
7.) A member array can only be apart of one Group
8.) Multiple members in the same pool stripe the data between them in proporation to their relative sizes. So if one member of two in a pool is 10x the size of the other it will have 10x the amount of data on it. So it will handle the greater percentage of the load.
9.) You can move volumes between pools at any time.
10.) If you move a member to another pool, all data is removed from that member first. So the remaining members of that pool must have enough free space.
11.) You can merge Groups, so to move a member from one group to another it must be removed from the starting group first. When you delete a member, it will automatically reset the member for you. If that member is in a pool with other members you will again need enough free space to hold that members data.
12.) When moving a member to another pool you can't chose which volumes.
13.) Volume and pool moves are seemless to all hosts. There is a potential performance impact during the move.
re: Storage Cluster. I think you are referring to Storage I/O Control? SIOC. If so, then we suggest that you don't use SIOC. Volume data is abstracted in ways that the ESXi host doesn't track. The EQL software is much more granular in balancing out I/O.
Origin3k
4 Operator
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1.8K Posts
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February 19th, 2014 09:00
Some minor comments:
- Modells comes with 12 - 48 disks
- Up to 8 members within a single pool
- Yes... Storage Cluster is always a good thing because it makes management easier on vSphere if you have a higher number of datastroes. BUT you have to disabled SIOC because this will confuse the EQL ALB. If you have two smart "things" at the end of a pipe bad things can be happend. We use vSphere Storage cluster for smart placements of VM/vDISK with a 90% boundary. The automatic svMotion is disabled and only a alarm will be raised to the admin can decide.
Regards,
Joerg
Dev Mgr
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February 20th, 2014 11:00
A few more comments:
11.) -> You cannot really 'merge' groups. To merge typically means 'with data in place'. With Equallogic you have to remove a member (enclosure) from a group before you can add it to another group. This means data will not be retained (on that or those member(s)).
10 + 12 -> You can move a member to another pool, but this moves only the member, you cannot select to move 1 or more volumes with it (at the same time), so you indeed need to have enough room on the source pool to be able to remove the member, and once the member has evacuated all its data (volumes), and has moved to the destination pool, you can then move any volumes you want to move (to that destination pool).
2.) -> If your group consists of 2 members of the '4k-series' (e.g. PS4000, PS4100, PS4110, PS M4110), you cannot add any additional members to the group unless you are adding a non-4k series unit (e.g. PS6100). After adding at least 1 non-4k unit you can add additional 4k units again. A group with only 4k units also has lower limits on the number of snapshots, replications, etc (see the configuration guide for the table of limits).
Origin3k
4 Operator
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1.8K Posts
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February 20th, 2014 11:00
The Configuration guide en.community.dell.com/.../DellEqualLogicConfigurationGuide_5F00_v14.4.pdf is here.
Regards,
Joerg
wadet5k
24 Posts
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February 23rd, 2014 20:00
Best source for all your questions:
psonlinehelp.equallogic.com/.../groupmanager.htm