RavenShadow
n00b
- Joined
- May 22, 2006
- Messages
- 20
sub.mesa has posted several times on his theories of record size vs stripe size and their relationship to performance of ZFS RAID pools. I'm wondering if anyone has taken his ideas into account when designing their RAID-Z3 configurations:
http://hardforum.com/showthread.php?p=1036154326&highlight=128+KiB#post1036154326
http://hardforum.com/showpost.php?p=1036395973&postcount=63
With the above stated, what are the ideal sizes for a RAID-Z3 pool?
4 and 5 disk RAID-Z3 pools seem small. 7 seems borderline (not much different than just going with RAID 1) as far as useable space vs # of drives goes. However an 11-disk RAID-Z3 has 16KiB writes which is smaller than the ideal indicated by sub.mesa of 32KiB - 128KiB.
The Solaris Internals Wiki recommends that RAIDZ3 configurations should start with at least 8 drives (5+3): http://www.solarisinternals.com/wik...onfiguration_Requirements_and_Recommendations
What have others done with their RAID-Z3 pools? What are recommended configurations and what type of performance impact would there be if I were to just go with an 8 drive RAID-Z3:
8-disk RAID-Z3 = 128 / 5 = 25.6
http://hardforum.com/showthread.php?p=1036154326&highlight=128+KiB#post1036154326
So which combinations would be good with 4K drives?
3-disk RAID-Z = 128 / 2 = 64KiB
4-disk RAID-Z2 = 128 / 2 = 64KiB
5-disk RAID-Z = 128 / 4 = 32KiB
6-disk RAID-Z2 = 128 / 4 = 32KiB
9-disk RAID-Z = 128 / 8 = 16KiB
10-disk RAID-Z2 = 128 / 8 = 16KiB
http://hardforum.com/showpost.php?p=1036395973&postcount=63
The problems i see is when the 128KiB get's spread over too many disks:
128KiB for 10-disk RAID-Z2 = 128KiB / 8 = 16KiB. Ideally you want drives to be handling chunks of 32KiB - 128KiB for optimal performance.
With the above stated, what are the ideal sizes for a RAID-Z3 pool?
Code:
128KiB / (nr_of_drives - parity_drives) = maximum (default) variable stripe size
4-disk RAID-Z3 = 128 / 1 = 128
5-disk RAID-Z3 = 128 / 2 = 64
7-disk RAID-Z3 = 128 / 4 = 32
11-disk RAID-Z3 = 128 / 8 = 16
4 and 5 disk RAID-Z3 pools seem small. 7 seems borderline (not much different than just going with RAID 1) as far as useable space vs # of drives goes. However an 11-disk RAID-Z3 has 16KiB writes which is smaller than the ideal indicated by sub.mesa of 32KiB - 128KiB.
The Solaris Internals Wiki recommends that RAIDZ3 configurations should start with at least 8 drives (5+3): http://www.solarisinternals.com/wik...onfiguration_Requirements_and_Recommendations
What have others done with their RAID-Z3 pools? What are recommended configurations and what type of performance impact would there be if I were to just go with an 8 drive RAID-Z3:
8-disk RAID-Z3 = 128 / 5 = 25.6