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RAID throughput on FusionIO

 | March 24, 2010 |  Posted In: Benchmarks, MySQL


Along with maximal possible fsync/sec it is interesting how different software RAID modes affects throughput on FusionIO cards.

In short conclusion, RAID10 modes really disappoint me, the detailed numbers to follow.

To get numbers I run

test with 16KB page size, random read and writes, 1 and 16 threads, O_DIRECT mode.

FusionIO cards are the same as in the previous experiment, as I am running XFS with nobarrier mount options.

OS is CentOS 5.3 with 2.6.18-128.1.10.el5 kernel.

For RAID modes I use:

  • single card ( for baseline)
  • RAID0 over 2 FusionIO cards
  • RAID1 over 2 FusionIO cards
  • RAID1 over 2 RAID0 partitions (4 cards in total)
  • RAID0 over 2 RAID1 partitions (4 cards in total)
  • special RAID10 mode with n2 layout

Latest mode you can get creating RAID as:

In this case for all modes use 64KB chunk size ( different chunk sizes also interesting question).

There is graph for 16 threads runs, and raw results are below.

As expected RAID1 over 2 disks shows hit on write throughput comparing to single disk,
but RAID10 modes over 4 disks surprises me, showing almost 2x drops.

Only in RAID10n2 random reads skyrocket, while writes are equal to single disk.

This makes me asking if RAID1 mode is really usable, and how it performs
on regular hard drives or SSD disks.

The performance drop in RAID settings is unexpected. I am working with Fusion-io engineers to figure out the issue.

The next experiment I am going to look into is different page sizes.

Raw results (in requests / seconds, more is better):

single disk
read/1 12765.49
read/16 31604.86
write/1 14357.65
write/16 32447.07
raid0 2 disks
read/1 12046.12
read/16 57410.58
write/1 12993.91
write/16 43023.12
raid1 2 disks
read/1 11484.17
read/16 51084.02
write/1 9821.12
write/16 15220.57
raid1 over raid0 4 disks
read/1 10227.13
read/16 61392.25
write/1 7395.75
write/16 13536.86
raid0 over raid1 4 disks
read/1 10810.08
read/16 66316.29
write/1 8830.49
write/16 18687.97
raid10 n2
read/1 11612.89
read/16 99170.51
write/1 10634.62
write/16 31038.5

Script for reference:

Vadim Tkachenko

Vadim Tkachenko co-founded Percona in 2006 and serves as its Chief Technology Officer. Vadim leads Percona Labs, which focuses on technology research and performance evaluations of Percona’s and third-party products. Percona Labs designs no-gimmick tests of hardware, filesystems, storage engines, and databases that surpass the standard performance and functionality scenario benchmarks. Vadim’s expertise in LAMP performance and multi-threaded programming help optimize MySQL and InnoDB internals to take full advantage of modern hardware. Oracle Corporation and its predecessors have incorporated Vadim’s source code patches into the mainstream MySQL and InnoDB products. He also co-authored the book High Performance MySQL: Optimization, Backups, and Replication 3rd Edition.


  • RAID 10,f2 is generally considered to be the overall fastest Linux RAID10, so you might want to try that. Also, as of mdadm 3.1.1, default chunk size is 512K rather than 64K, so maybe that’s worth trying.

  • Vadim,

    Why do you expect RAID1 to be slower than single disk for writes ? Normally 2 disk RAID1 should be twice the speed for random reads and about same speed for random writes. You have to do 2 writes per write but there are 2 devices to do them in parallel.

  • An answer for why writes to RAID1 are slower than a single drive: for RAID1, the time for the write to complete is dependent on the slowest of the two devices at doing the write. For hard drives, this is easier to think about because of rotational delay and servo motors. With a single drive, sometimes you get lucky and the head is near where the write needs to happen. With RAID1, now you have two drives that need to have their heads conveniently positioned before you can get lucky. I assume there’s a significant variance in the amount of time a FusionIO device can take to complete a write.

  • I understand Fusion IO can be configured in “basic/full-capacity” mode and some sort of “performance/diminished-capacity” mode. ?? were these benchmarks done under basic/or/performance mode (apologies if I am using the wrong terms)

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