Ceph storage Disk IOPS Common sense

Three factors for calculating disk IOPS:

1. Read and write ratio of RAID type

IOPS calculation formula for different RAID types:

RAID type	Formula
RAID5, RAID3	Drive Iops=read ioPS + 4*write ioPS
RAID6	Drive Iops=read ioPS + 6*write ioPS
RAID1, RAID10	Drive Iops=read ioPS + 2*write ioPS

2. The IOPS value of the hard disk type

IOPS for different disk types:

Hard disk Type	IOPS
FC 15K RPM	180
FC 10K RPM	140
SAS 15K RPM	180
SAS 10K RPM	150
SATA 10K RPM	290
SATA 7.2K RPM	80
SATA 5.4K RPM	40
Flash Drive	2500

device	iops	notes
rpm sata HDD	~75-100 Iops[2]	sata 3  gbit/s
10,000 rpm SATA drives	HDD	~125-150 Iops[2]	sata 3 gbit/s
sas HDD	~140 iops[2]	sas
15,000 rpm SAS drives	HDD	~175-210 IOPS[2]	Sas

3, the specific business system read and write ratio

Second, the case

1) Business requirements: 10TB FC 15K rpm storage space, meet 6000 IOPS, calculate RAID5,RAID10 How many hard drives are required?

First you need to know the percentage of read and write operations in I/O.   Assume 6000 iops read / write ratio is 2 : 1

The actual IOPS load for different RAID type drive Drives is as follows:

RAID10: (2/3) *6000+2* (1/3) *6000= 8000 IOPS

RAID5: (2/3) *6000+4*(1/3)*6000=12000 IOPS

Depending on the IOPS value of the different hard disk types, the number of disks required is calculated:

raid10:8000 /180 = block

raid5:12000/180 =67 block

2) A RAID5, consisting of 5 500G 10K rpm FC disks, to calculate the maximum IOPS supported by this raid and the IOPS available to the front-end application?

First 10K rpm FC disk, the IOPS of a single disk is 140, 5 disk maximum IOPS value is 700.

Assuming a read-write ratio of 2:1, the IOPS available to the front-end application are:

(2/3) *x+4* (1/3) *x = 700

2*x = 700

x=350

The IOPS available to the front-end application is 350.

(Input/output Operations per Second), that is, the higher the number of read-write (I/O) operations per second, the faster the read (write) data. Can not be set, is the factory has been fixed.

Ceph storage Disk IOPS Common sense