ChrisReeve
Explorer
- Joined
- Feb 21, 2019
- Messages
- 91
Good morning.
This really shouldn't be new information to anyone, but I see this incorrectly being claimed here on a daily basis. Stream writes are not limited to single drive performance. I believe this misunderstanding stems from users mixing stream read/write with IOPS, which are limited to single drive performance.
Stream read/write are limited to N-p, where N = total number of drives in vdev, and p = number of parity drives.
Example:
I have a RAIDz2 pool consisting of one vdev, with 10x10TB WD100EMAZ drives. Assuming a performance of 250IOPS and ~180MB/s per drive, the theoretical maximum) performance is:
Stream read: 1440MB/s
Stream write: 1440MB/s
IOPS: 250.
There are of course other bottlenecks, and for the system in question, running a Xeon E5-2650v2 (2,6GHz base, 3,3GHz boost, 64GB RAM, no cache drive, pool is both encrypted and compression enabled), I see sustained writes for several hundred gigabytes in excess of 600MB/s over SMB (about 260GB divided between 13 large video files)
Again, this is not new information, but there are still a massive number of users incorrectly claiming otherwise. Please stop spreading misinformation.
Source: https://www.ixsystems.com/blog/zfs-pool-performance-2/
This really shouldn't be new information to anyone, but I see this incorrectly being claimed here on a daily basis. Stream writes are not limited to single drive performance. I believe this misunderstanding stems from users mixing stream read/write with IOPS, which are limited to single drive performance.
Stream read/write are limited to N-p, where N = total number of drives in vdev, and p = number of parity drives.
Example:
I have a RAIDz2 pool consisting of one vdev, with 10x10TB WD100EMAZ drives. Assuming a performance of 250IOPS and ~180MB/s per drive, the theoretical maximum) performance is:
Stream read: 1440MB/s
Stream write: 1440MB/s
IOPS: 250.
There are of course other bottlenecks, and for the system in question, running a Xeon E5-2650v2 (2,6GHz base, 3,3GHz boost, 64GB RAM, no cache drive, pool is both encrypted and compression enabled), I see sustained writes for several hundred gigabytes in excess of 600MB/s over SMB (about 260GB divided between 13 large video files)
Again, this is not new information, but there are still a massive number of users incorrectly claiming otherwise. Please stop spreading misinformation.
Source: https://www.ixsystems.com/blog/zfs-pool-performance-2/