Will I see a write performance increase going from single disk to CentOS Software RAID10? Any industry estimates on the % increase?

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    How many drives and how are they arranged? – David Schwartz Sep 18 '13 at 4:00

RAID 10 provides both reliability and performance by mirroring and striping.

RAID 10 can provide up to N/2 in performance, both throughput and IO, where N is the number if drives in array, capacity will be about 1/2 of total. i.e. in case of 10 drives of 500GB capacity it can provide up to 500% of performance of single drive and ca. 2.5 TB of array capacity and can sustain failure of up to 5 drives (if drives do not share same segments).

RAID 10 requires at least 4 drives (2-drive RAID 10 actually is RAID 1, 3-drive RAID 10 is RAID 1E).

Linux kernel RAID (mdraid) implements three layouts of placing chunks, each of them have impact on performance, imbalance between Read and Write in case of non-linear, random operations.

More general details on Wikipedia

Performance information, benchmarks, tests (Kernel official)

mdraid wiki (Kernel official)

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  • The last link shows benchmarks where RAID1 has slightly better write performance than RAID10. How's that possible? – user3180 Sep 18 '13 at 12:34
  • In worst case - might be. Where's that? – GioMac Sep 18 '13 at 12:35
  • I suggest just using "--level=raid10 --layout=n2", which is the middle of the road. For sequential reads/writes you will get pretty close to N/2. For random read/writes you might only see 1/10th of that number, but it will be better then if it was a single-disk or RAID-1. The limiting factor in random-access is IOPS or seeks/second that the drives are capable of. More spindles helps, but can only do so much. – tgharold Sep 28 '13 at 4:19
  • IOPS is not equal to seek/sec. – GioMac Sep 28 '13 at 9:30

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