Raid5 performance versus single drive

theinv

Limp Gawd
Joined
Apr 17, 2008
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Assuming we have a decent hardware raid controller from Areca/3Ware. Is the read/write speed in a RAID5 setup with 4 or 8 drives is always faster than single drive?
 
Assuming we have a decent hardware raid controller from Areca/3Ware. Is the read/write speed in a RAID5 setup with 4 or 8 drives is always faster than single drive?

If you want to guarantee that A is always faster than B you have to test all types of workload and all types of drives.

I will say that with 4-8 HDDs in RAID5 on a good Areca (or similar) controller you will get much better sequential read/write speeds than a single drive (of the same type) can provide. Add some cache to that controller and you will get good performance for many typical file access patterns.

What do you want to use this system for?
 
read performance on RAID5 should be the same as RAID0

sequential write performance on RAID5 is maximum of (number_of_disks - 1) * <sequential write speed per disk>. With a reasonable RAID5 engine you should be able to get at least half of this theoretical maximum.

So yes, its faster.
 
If you want to guarantee that A is always faster than B you have to test all types of workload and all types of drives.

I will say that with 4-8 HDDs in RAID5 on a good Areca (or similar) controller you will get much better sequential read/write speeds than a single drive (of the same type) can provide. Add some cache to that controller and you will get good performance for many typical file access patterns.

What do you want to use this system for?

It is for photo and video editing.

I am just wondering whether I should get a single 7200RPM drive or a few 5400RPM green drive. If RAID5 is faster than single drive, it means 4 x 5400RPM in RAID5 should have equal or faster performance than a single 7200RPM, right?
 
'faster' in which sense?
Throughput yes
random read yes
random write no
latency/access time no
 
It is for photo and video editing.

I am just wondering whether I should get a single 7200RPM drive or a few 5400RPM green drive. If RAID5 is faster than single drive, it means 4 x 5400RPM in RAID5 should have equal or faster performance than a single 7200RPM, right?

I'd rather buy a SSD and use that as working disk if your projects aren't too large. Then get a conventional HDD to use for archival storage, and also remember a backup solution.
 
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