This post is more than 5 years old
1 Rookie
•
8 Posts
0
20590
July 5th, 2017 03:00
Compellent default RAID Options | Disk quantity sizing
Hi,
I have a question regarding the compellent default RAID levels (RAID 5-5, 5-9,6-6, 6-10), for example if I design SC4020 with 24 disks:
Q#1 If I configure dual redundancy with RAID level RAID 6-10, does it mean that there will be two sets of RAID 6 on each 10 disks? if yes then what happens to the remaining 4 disks?
Q#2 If I configure dual redundancy with RAID level RAID 6-6, does it mean that there will be 4 sets of RAID 6 on each 6 disks? if yes then total parity disks will be 2+2+2+2=8?
No Events found!
CompellentSanAd
43 Posts
2
July 11th, 2017 19:00
So with Compellent all data is striped across all disks. If you have 24 disks, and assign 2 as Hot Spares you will have 22 disks left to configure. When you configure RAID you will either set single or dual redundancy. Either way the RAID parity is striped across all disks. So all disks have Raid Extents in them whether it is Single Redundancy (Raid 10, Raid 5-5, Raid 5-9) or dual Redundancy (Raid 10 DM, Raid 6-6, Raid 6-10).
Dual Redundancy is required for disks larger than 1.9 TB in size. If your disks are smaller than you could use Single Redundancy. Reference page 8 of:
Understanding RAID with Dell SC Series Storage
http://en.community.dell.com/techcenter/extras/m/white_papers/20442059
DELL-Sam L
Moderator
•
7.6K Posts
2
July 5th, 2017 14:00
Hello arabid,
Here is the breakdown on how Raid works on your SC4020:
RAID 6-6 (4 data segments, 2 parity segments for each stripe)
RAID 6-10 (8 data segments, 2 parity segments for each stripe)
Here is a link to a white paper that also provides more info on the raid setup. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj89vCXg_PUAhWrqFQKHXxyDS8QFggmMAA&url=http%3A%2F%2Fen.community.dell.com%2Ftechcenter%2Fextras%2Fm%2Fwhite_papers%2F20442059&usg=AFQjCNF2ecjaIMjMmZW9CMUe7N6cn5HtMw
Please let us know if you have any other questions.
AR_ABID
1 Rookie
•
8 Posts
0
July 5th, 2017 23:00
Hi SAM,
Thanks for the reply, your answers are always very helpful to me, your reply above is very clear to me but I have confusions, I am highlighting them in my questions, this explanation is not available in the provided document.
Q#1 If I configure dual redundancy with RAID level RAID 6-10 on 24 disks, does it mean that there will be two sets of RAID 6 on each 10 disks? if yes then what happens to the remaining 4 disks?
Q#2 If I configure dual redundancy with RAID level RAID 6-6 on 24 disks, will I lose capacity of 8 disks in parity? this is very important to know for sizing the capacity.
DELL-Sam L
Moderator
•
7.6K Posts
0
July 6th, 2017 09:00
Hello arabid,
Q#1 If I configure dual redundancy with RAID level RAID 6-10 on 24 disks, does it mean that there will be two sets of RAID 6 on each 10 disks? Yes. if yes then what happens to the remaining 4 disks? With the last 4 disk you can create another raid to use them if you would like.
Q#2 If I configure dual redundancy with RAID level RAID 6-6 on 24 disks, will I lose capacity of 8 disks in parity? Yes that is correct. When using RAID 6-6 you will have 2 parity disk for each RAID. this is very important to know for sizing the capacity.
Please let us know if you have any other questions.
Mohamed-Gaber
1 Rookie
•
11 Posts
0
August 8th, 2021 12:00
As I understood, for RAID 6-10, 6 is the RAID level and 10 is the summation of the segments (6 data and 4 parity). RAID 6-6, 6 is the RAID level and 6 is the summation of the segments (4 data and 2 parity)
Mohamed-Gaber
1 Rookie
•
11 Posts
0
August 8th, 2021 12:00
Do this mean that RAID 6-6 writes on 2/3 of the disk space after removing the spare two disks.? And same, RAID 6-10 writes on 80%? I notice that alwase there is half of a disk subtracted.
DELL-Chris H
Moderator
•
9.5K Posts
0
August 9th, 2021 07:00
Mohamed-Gaber,
That's correct regarding the raid levels and segment analysis, but the percentage of the drives would differ depending on the number of drives in the Virtual Disk, as well if the 2 parity drives are removed it would fail the Virtual Disk.
Let me know if this helps.