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With disks having TB of capacity, the rebuild time also increases, RAID 6 can reduce this risk
I think, RAID 5 is better for smaller Companies where data priority is less then data availabilty.
Other side RAID 6 is better for large data storage, where every data is critical.
Other side RAID 6 is better for large data storage, where every data is critical.
Considering that I'm not going to be rebuilding disk more often that I will need to write to them, i will still have to choose RAID5. Performance is more important to me than rebuild times. Plus, the added cost just isn't justified.
-Leo
-Leo
Once where 2 disks failed at the same time and another time, a second disk failed during Rebuild, so sometimes RAID6 DOES make sense.
Drawing the correct image for RAID-5 with 4 disks, eh?
The distributed parity requires 1/N space on each disk, where N is the number of disks in array.
Same remark for RAID-6. Since you have 4 disks, each disk is divided in 4 areas, only.
Otherwise, the advantage of using RAID-6 for large ammounts of data, is correct.
The distributed parity requires 1/N space on each disk, where N is the number of disks in array.
Same remark for RAID-6. Since you have 4 disks, each disk is divided in 4 areas, only.
Otherwise, the advantage of using RAID-6 for large ammounts of data, is correct.
RAID 5 is better when used on Database systems, and may be less expensive
Many times, the choice of RAID comes down to software and hardware support. When RAID-6 isn't supported, it becomes a choice of "use what you have" VS "buy a new controller card."
On our last non-recoveable RAID-5 experiance, we opted to do RAID-10. Our controller card could do it, but not RAID-6, and we would have enough storage in that configuration, with the hard drives we had.
RAID-10 is very redundant, so very hard to kill. It also could be considered wasteful, but drives are cheap too.
The actual read/write speeds will depend on the controller card's processor, and hard drives used.
On our last non-recoveable RAID-5 experiance, we opted to do RAID-10. Our controller card could do it, but not RAID-6, and we would have enough storage in that configuration, with the hard drives we had.
RAID-10 is very redundant, so very hard to kill. It also could be considered wasteful, but drives are cheap too.
The actual read/write speeds will depend on the controller card's processor, and hard drives used.
I don't understand the reasoning in the original article, why sacrifice performance to reduce disk rebuild times (a rare occurrence)? If you need more redundancy and quicker rebuilds than RAID 5 you should be using RAID 10, most storage vendors I've discussed it with hate the idea of RAID 6 - they just had to add support for it because their competitors supported it and poorly informed end users bought into the smoke and mirrors.
Too many organizations can't justify the overhead, or more importantly the funds, to get that extra level -> But you are correct, RAID 1+0 is the next best way to go.
The company for which I work has thousands of backup appliances in the field from which we get a tremendous amount of data concerning this subject. After years using RAID-5, we now ship only RAID-1 in our low-end appliances, RAID-10 in our medium-end appliances, and RAID-6 (actually, RAID-1/RAID-6) in our higher-end appliances.
In the real world, with larger disks, the major reason that you end up going to RAID-6 over RAID-5 is the concern with respect to drive failure during in-operation rebuild.
__________________
Mark Campbell
http://www.unitrends.com/
In the real world, with larger disks, the major reason that you end up going to RAID-6 over RAID-5 is the concern with respect to drive failure during in-operation rebuild.
__________________
Mark Campbell
http://www.unitrends.com/
When you say large storage for RAID6 how much storage do you refer to? I would like to have an idea of the large storage range please.
With RAID 5, you lose the space of 1 drive (for parity). In RAID 6, you lose the space of two drives. For example, using RAID 5 in an array with (16) 1TB drives, your total available RAW space would be 15TB. Using RAID 6, your total available RAW space would be 14TB.
For the most part you lose nearly 1/3rd of total space for RAID5 and due to higher levels of compression with RAID 6, it's slightly more due to the fact that the Parity structure is doubled. Raid 5 requires a minimum of 3 drives and Raid 6 requires 4, the compression algorithm's get better with the more drives you add, especially with RAID 6, but RAID 6 will always use more space for Parity than RAID 5, but less than RAID 10, so it's a good balance for those who want to have 4 drives or more with better protection than RAID 5 without losing quite as much space.
Hello Rick,
What is impact on file server (read) when we use RAID6 (in place of RAID5) ?
How to compensate write performance issue of RAID6? Can we add new disks?
Regards
Ganesh
What is impact on file server (read) when we use RAID6 (in place of RAID5) ?
How to compensate write performance issue of RAID6? Can we add new disks?
Regards
Ganesh
Assuming your System Bus can handle the extra bandwidth, the more drives you have the better the Read performance is. Let's say you have SATAII 300Mbps disks, with RAID 5, you're reading data off 2 disks simultaneously, so your actual throughput is closer to 600Mbps and with RAID6 it's closer to 900Mbps. Unless a drive has failed, Read requests don't touch the Parity bits, which in the case of RAID5 it's 1 stripe of Parity and with RAID6, it's two.
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