Difference between revisions of "Disk Options and Comparisons"
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| − | == | + | == RAID0 == |
| − | + | ||
| − | + | RAID0 gives the option to provide better read/write performance. Although it is not the best option for reliability. | |
| − | + | The SSD used is OCZ Vertex2 120GB (Measured 230 MB/s write and 275 MB/s read throughput on Atom D510MO motherboard) | |
| − | + | RAID0 was built both on Core 2 and Atom D510. | |
| − | However 2 disks RAID0 was installed on Atom D510 but only | + | |
| + | |||
| + | === Core 2 === | ||
| + | |||
| + | 2 disks RAID0 was installed on Core2 and achieved measured 469 MB/s write throughput. It is the value close to double of single disk performance. | ||
| + | |||
| + | === Atom D510 === | ||
| + | |||
| + | * SATA was treated as IDE | ||
| + | |||
| + | However 2 disks RAID0 was installed on Atom D510 but only 304 MB/s read throughput when testing md0. The results shows far less than expected double performance. | ||
Atom D510 uses DMI bus which has theoretical limit 10Gb/s. It needs at least four SSDs to saturate and is not the bottleneck. | Atom D510 uses DMI bus which has theoretical limit 10Gb/s. It needs at least four SSDs to saturate and is not the bottleneck. | ||
| + | |||
| + | Interesting result through testing read throughput from reading from two disks at them same time, shows a rough read throughput over 450 MB/s. This test indicate that RAID0 throughput was limited by internal software bottleneck. | ||
| + | |||
| + | * Change SATA settings to ACHI without rebuild RAID0 | ||
| + | |||
| + | Speed was not obviously affected. | ||
| + | |||
| + | * Interrupts | ||
| + | |||
| + | cat /proc/interrupts | ||
| + | |||
| + | I found that all interrupts go to processor 0. Run following command to balance interrupts | ||
| + | |||
| + | sudo bash -c "echo '3'> /proc/irq/19/smp_affinity " | ||
| + | |||
| + | Read throughput on RAID0 /dev/md0 achieves 348 MB/s | ||
| + | |||
| + | * Create 10GB large file and read directly | ||
| + | |||
| + | Read throughput on RAID0 achieves 438 MB/s | ||
| + | |||
| + | * SATA was treated as Advanced Host Controller Interface (AHCI) and RAID0 was rebuilt | ||
| + | |||
| + | Read throughput on md1 achieves 520 MB/s and write achieves 318 MB/s, which are within the expectation. | ||
| + | |||
| + | == RAID1 == | ||
| + | |||
| + | Read throughput achieved on Atom D510 platform was only 189 MB/s, far less than expected more than 400 MB/s. | ||
| + | |||
| + | Write throughput was 177 MB/s. | ||
Latest revision as of 01:41, 4 October 2011
We have 3 disk options that conform with the low power requirement (< 2-3 Watts?):
To compare options amongst these drives, we need common parameters that give us a decent and standard metric. Some parameters are:
- Power Consumption (Idle and Peak)
- Read/Write Speed (Data Transfer Rate)
- Sequential Data
- Random Data
- Cost per Gigabyte
- I/O Interface Support and Bottlenecks
- PCIe
- USB 2.0/3.0
- SD/MMC
Contents |
RAID0
RAID0 gives the option to provide better read/write performance. Although it is not the best option for reliability.
The SSD used is OCZ Vertex2 120GB (Measured 230 MB/s write and 275 MB/s read throughput on Atom D510MO motherboard)
RAID0 was built both on Core 2 and Atom D510.
Core 2
2 disks RAID0 was installed on Core2 and achieved measured 469 MB/s write throughput. It is the value close to double of single disk performance.
Atom D510
- SATA was treated as IDE
However 2 disks RAID0 was installed on Atom D510 but only 304 MB/s read throughput when testing md0. The results shows far less than expected double performance.
Atom D510 uses DMI bus which has theoretical limit 10Gb/s. It needs at least four SSDs to saturate and is not the bottleneck.
Interesting result through testing read throughput from reading from two disks at them same time, shows a rough read throughput over 450 MB/s. This test indicate that RAID0 throughput was limited by internal software bottleneck.
- Change SATA settings to ACHI without rebuild RAID0
Speed was not obviously affected.
- Interrupts
cat /proc/interrupts
I found that all interrupts go to processor 0. Run following command to balance interrupts
sudo bash -c "echo '3'> /proc/irq/19/smp_affinity "
Read throughput on RAID0 /dev/md0 achieves 348 MB/s
- Create 10GB large file and read directly
Read throughput on RAID0 achieves 438 MB/s
- SATA was treated as Advanced Host Controller Interface (AHCI) and RAID0 was rebuilt
Read throughput on md1 achieves 520 MB/s and write achieves 318 MB/s, which are within the expectation.
RAID1
Read throughput achieved on Atom D510 platform was only 189 MB/s, far less than expected more than 400 MB/s.
Write throughput was 177 MB/s.
