StitchExperimen
Dabbler
- Joined
- Mar 22, 2014
- Messages
- 10
This quote is from another forum.
My question is after the quote.
http://hardforum.com/showpost.php?s=8d31305e57c1dd2853eb817124ff18d9&p=1036865233&postcount=3
Quote
EDIT2: A note on performance:
The Write-IOPS that a single vdev can produce is limited to the IOPS of the single slowest drive in the vdev. This is because each member of a vdev must sign off on any changes made to any files on that vdev, and the operation is performed individually. If you want more performance, add additional vdevs to the zpool, rather than making a single larger vdev.
For example: you have 6x2TB drives. in a single RAID-Z2 vdev, you have 12TB zpool, 8TB space. You could instead create 2 RAID-Z1 vdevs: 3x2TB each, leaving you the same 8TB of usable space out of your 12TB zpool, one parity disk per vdev. However, in this configuration, you would have 2x the IOPS, as IOPS are the aggregate of the single slowest drive from each vdev. If you wanted to retain RAID-Z2, you would need to add 2 additional 2TB drives, bringing you to 8x2TB, 16TB pool, 8TB space: 4x2TB per vdev, 2 parity instances per vdev, and 2x the IOPS of your original configuration. To maximize IOPS, you could skip RAID-Z entirely, and instead mirror your disks: 2x2TB mirrors per vdev, 3 vdevs, so 6TB and 3x the IOPS. No parity per-se, but still fault tolerant per vdev. The RAM requirement of this configuration would be significantly less as no parity data would be calculated. More importantly, you can always add additional vdevs to the zpool, but no vdev can be expanded. This means you could add additional storage space to your zpool by simply adding pairs of disks. During a data-reconstruction and resilvering, only the contents of the mirrored drive would have to be rewritten, rather than the entire zpool. This means a quicker recovery.
End quote
If I was to make two RAID-Z2 would I have to stripe them for twice the read boost and does the write of the drives double? And what if I was to make three RAID-Z2?... would I get 3 times the performance. Or would this have to go under the category of raid 10, using RAID-Z2s and what is the limit of stacking vdevs before there is no more benefit to speed?
My question is after the quote.
http://hardforum.com/showpost.php?s=8d31305e57c1dd2853eb817124ff18d9&p=1036865233&postcount=3
Quote
EDIT2: A note on performance:
The Write-IOPS that a single vdev can produce is limited to the IOPS of the single slowest drive in the vdev. This is because each member of a vdev must sign off on any changes made to any files on that vdev, and the operation is performed individually. If you want more performance, add additional vdevs to the zpool, rather than making a single larger vdev.
For example: you have 6x2TB drives. in a single RAID-Z2 vdev, you have 12TB zpool, 8TB space. You could instead create 2 RAID-Z1 vdevs: 3x2TB each, leaving you the same 8TB of usable space out of your 12TB zpool, one parity disk per vdev. However, in this configuration, you would have 2x the IOPS, as IOPS are the aggregate of the single slowest drive from each vdev. If you wanted to retain RAID-Z2, you would need to add 2 additional 2TB drives, bringing you to 8x2TB, 16TB pool, 8TB space: 4x2TB per vdev, 2 parity instances per vdev, and 2x the IOPS of your original configuration. To maximize IOPS, you could skip RAID-Z entirely, and instead mirror your disks: 2x2TB mirrors per vdev, 3 vdevs, so 6TB and 3x the IOPS. No parity per-se, but still fault tolerant per vdev. The RAM requirement of this configuration would be significantly less as no parity data would be calculated. More importantly, you can always add additional vdevs to the zpool, but no vdev can be expanded. This means you could add additional storage space to your zpool by simply adding pairs of disks. During a data-reconstruction and resilvering, only the contents of the mirrored drive would have to be rewritten, rather than the entire zpool. This means a quicker recovery.
End quote
If I was to make two RAID-Z2 would I have to stripe them for twice the read boost and does the write of the drives double? And what if I was to make three RAID-Z2?... would I get 3 times the performance. Or would this have to go under the category of raid 10, using RAID-Z2s and what is the limit of stacking vdevs before there is no more benefit to speed?
