Hello guys, currently, I have Mean Object Size: 21.66 KB
At the moment, I have 3 SCSI disks, 36 GB, 10K, so my cache_dir is:
cache_dir aufs /cache/cache1 28000 60 256 cache_dir aufs /cache/cache2 28000 60 256 cache_dir aufs /cache/cache3 28000 60 256
There is no RAID. Because my Mean Object Size is 21 K, it means, there is 28000000/21/60/256 = 88 files in each second-level directory (which is few, I didn't expect the mean object size so high, but I don't think it is a disadvantage).
My boss just gave me another two SCSI disk, 70 GB, 15K - he wants me to maximise "Byte hit ratio" and I believe to have bigger cache is the right way (I have already set LFUDA replacement policy etc).
I am going to add these two disk to the box, how would you use them, so you get the best performance?
1) add 2 new cache_dirs 56 GB cache on every from these two 70GB disks?
cache_dir aufs /cache/cache4 56000 60 256 cache_dir aufs /cache/cache5 56000 60 256
If my mean object size stays 21 kb, there will be average 173 files (56000000/21/60/256) in each second-level directory.
2) add 4 new cache_dirs two 28 cache on every from these two 70GB disks?
cache_dir aufs /cache/cache4 28000 60 256 cache_dir aufs /cache/cache5 28000 60 256 cache_dir aufs /cache/cache6 28000 60 256 cache_dir aufs /cache/cache7 28000 60 256
I prefer the first solution, but does it realy matter?
I also wonder if there will be any trouble caused by my mix of three 36GB disk 10K only and two 70GB disks 15K working together...
Thank you, Marji
