Dell Equallogic PS6110 RAID configuration

[luisvieyra]

Hello, I'm new on SAN networks, I configured my equallogic with 24 1TB drives, however I only can select RAID 6, or 50 , which let my uso only 16.5 TB or less of free space, how come????

[minimoo]

https://data.technimax.cz/attach/artilky/Dell-EqualLogic-PS6000-config.pdf

 

The capacity on page 24 seems to match what you are getting.

 

I've used Dell's compellent stuff (which "doesn't use" RAID5/6/50 etc) - but does it's own thing; which seems to be to implement a virtual raid 1+raid 5/6 across the whole set of drives.

 

It looks like the equallogic brand may do similar:

(a) 24 and 48 drive arrays implement multiple RAID 6 sets within a single chassis.

 

So, looking at Page 31 - they imply they might do as follows:

 

1 Hot Spare

Raid 6 - 12 Disks (10 data + 2 parity)

Raid 6 - 11 Disks (9 data + 2 Parity)

 

So that would mean the capacity of the array is only going to be the capacity of 19 disks in the raid. If we then consider some drives show capacity as 1000 bytes, as opposed to 1024, i start to get around 17.7TB of usable space - not quite your 16.5tb, but hopefully something here might allow you to work out what it's actually doing

[Oaktech]

 

So that would mean the capacity of the array is only going to be the capacity of 19 disks in the raid. If we then consider some drives show capacity as 1000 bytes, as opposed to 1024, i start to get around 17.7TB of usable space - not quite your 16.5tb, but hopefully something here might allow you to work out what it's actually doing

 

Bear in mind formatted/usable capacity will always be less than quoted because of partition tables and offsets.

[minimoo]

yea, but wouldn't expect by a TB

[Steve21]

Normally with the old equallogics they also use about the equiv. 2 disks for logs/snapshots/eql database/reserve/config etc.

 

So in a normal EQL 24 bay with RAID6, you'd end up with 20 + 2(logs etc) + 2 hot-spares, meaning the 20 usable disks would be about 16.4TB~

 

I know in some editions of SAN HQ you used to be able to change the above, but generally that's as expected in terms of outcome

 

Steve