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83610
September 8th, 2014 08:00
Too Many Spare Drives When Creating Array
I will preface this by saying I am new to Equallogic SANs...
I have a PS6100 with 16 2TB drives. When doing the initial configuration on the array it is leaving 4 of the disks as "spare" no matter which RAID level I choose. The option to right click on the drive and choose "Add disk to RAID" is grayed out.
Having 4 drives/8TB of "spare" storage seems way too excessive. I would only want 1 or 2 hot spares. I don't know if there is a problem preventing the array from allowing them to be "online" or if there is a setting to specify the number of spares. If there is a setting, I can't find it anywhere.
Please advise if this is normal behavior or if there is anything I can do to get some of this extra space added to my array.
Thank you!
Origin3k
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2.3K Posts
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September 8th, 2014 08:00
Hmmmm
the old PS60x0 comes with 16x3.5". The PS61x0 and later comes as
24x 3.5"
12x 3.5"
or 24x 2.5"
So IIRC there is no modell with 16 disks.
Dell "removed" the RAID5 Option within one of the latest FW Version from the GUI, if a customer have 1TB disks or greater because the chance of a double disk failure increases when doing long ongoing raid rebuild with large disks.
If you would like to force the use of a RAID5 + Single Hotspare you have to create the raid leveln from the command line.
We use RAID50 for the older 16 disk modell which means: Usable Disks = Total Disks - 4 (2 Parity + 2 Hotspares)
Regards,
Joerg
colinjon76
2 Posts
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September 8th, 2014 09:00
Thank you for the response. Just so I can clarify, we have the PS6100 with 24x 3.5" drive bays, but only have 16 drives in the unit. Are you saying it will only configure an array using 12 or 24 drives - and maybe that's why these drives are not "online"?
When I create the volume with RAID 50, it says the total capacity is 17.76TB in the Equallogic. When I calculate 16 2TB drives with RAID 50 it says it should be 28TB (raw). This makes me think it really is only using 12 drives in the array (which would be 20TB raw).
Thoughts?
Origin3k
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2.3K Posts
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September 8th, 2014 13:00
Rule of thumb is that an EQL array is 50 or 100% populated and not something like 75%. For me its lools like the array dont use all disks because you dont have enough.
Regards,
Joerg