Chapter 2. Hardware configuration planning 39
failure by having a mirror copy of each disk. By combining the two, RAID 10 provides data
protection and good I/O performance.
2.8.4 Combination of RAID 5 and RAID 10 arrays
It is possible to have RAID 10 and RAID 5 arrays configured within the same loop or
enclosure, as illustrated in Figure 2-19.
Figure 2-19 RAID 5 and RAID 10 in the same loop
2.8.5 RAID 5 versus RAID 10 performance
You may be asking which is better, RAID 5 or RAID 10? As with most complex issues, the
answer is that it depends. There are a number of workload attributes that influence the
relative performance of RAID 5 versus RAID 10, including the use of cache, the relative mix of
read versus write operations, and whether data is referenced randomly or sequentially.
Random and sequential reads and random writes
When a storage server receives a read request from a host, the storage server first looks to
see if the requested data is in cache. If it is, there is no need to read the data from disk, and
so it does not matter whether RAID 5 or RAID 10 is used.
For reads which must be satisfied from disk, performance of RAID 5 and RAID 10 are roughly
equal, except at high I/O rates. If RAID 5 contains significantly more data than RAID 10 array,
data are located on the inside tracks of disks that it takes longer seek time that sometimes
RAID 5 become slower than RAID 10. But if RAID 5 contains almost same amount of data,
Note: If you make a RAID 5 array first and then make RAID 10 in the first or second
enclosure, three hot spare disks are made and it will reduce the total effective capacity. To
avoid this, you should create the RAID 10 Array in the first or second enclosure.
IBM
TotalStorage
RAID 5+10 configuration example
When using same capacity and rpm.
data spare
mirror
1
st
RAID10:3+3+2S
DA
DA
1750-511
1750-EX1-1
1750-EX1-3
1750-EX1-2
Loop 0
Loop 1
parity (float)
1
st
RAID5:6+P+S
2
nd
RAID10:3+3+2S
If first array is RAID 5 and second array is RAD10 in
first two enclosures, three hot spares are made.
2
nd
RAID5:7+P

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