Dell R720,E5-2620,16GB RAM,PERC H720P Mini (LSI SAS2208 ROC)
Red Hat Enterprise Linux Server release 6.3
General Parallel File System (GPFS) 3.5.0.11
Raid5:5个2.5" SAS2 10Krpm 600GB为一个Raid5做成一个NSD,用这个NSD做成一个GPFS文件系统

Iozone 3.414,测试命令iozone -i 0 -i 1 -i 2 -r 1m -s 64G,结果单位Kbytes/sec
write: 393595
rewrite: 406162
read: 431798
reread: 434553
random read: 97135
random write: 238970

Dell R720xd,E5-2620*2,32GB RAM,PERC H720P Mini (LSI SAS2208 ROC)
Red Hat Enterprise Linux Server release 6.3
General Parallel File System (GPFS) 3.5.0.7
SSD: Plextor M5pro 256GB
Iozone 3.414,测试命令iozone -i 0 -i 1 -i 2 -r 1m -s 64G,结果单位Kbytes/sec
说明:Dell PERC H720P是CacheCade 1.1,SSD只支持读缓存不支持写缓存

Raid1:2个2.5" SAS2 10Krpm 600GB组成Raid1,文件系统ext4

无CacheCade
write: 187650
rewrite: 186938
read: 175573
reread: 176657
random read: 70806
random write: 130185

有CacheCade
write: 189204
rewrite: 185290
read: 174780
reread: 175871
random read: 95549
random write: 129789

通过SSD缓存随机读取明显提升

Raid5:15个2.5" SAS2 10Krpm 900GB,每5个硬盘为一个Raid5共3个,每个Raid5在GPFS里面做成一个NSD,三个NSD做成一个GPFS文件系统

无CacheCade
write: 1017661
rewrite: 1010487
read: 1253673
reread: 1371768
random read: 103493
random write: 504399

有CacheCade
write: 469138
rewrite: 459371
read: 559042
reread: 566837
random read: 53655
random write: 362697

当SSD性能落后于被加速的机械硬盘时性能反而下降

CacheCade:可将热点数据自动迁移到SSD盘上,老的1.x版本只支持SSD用于读缓存,新的Pro 2.0支持SSD用于读写缓存。
FastPath:可以大幅度降低SSD的存取延迟。如果CacheCade可用则FastPath也一定可用,CacheCade需要FastPath。

强烈建议仔细阅读:https://sites.google.com/a/storaid.org/storaid/storage-raid/lsi-raid-software-stack/megaraid-stack