How can I improve my read hit rate?
Posted: Tue Feb 05, 2013 5:21 am
Here is my setup:
H/W
16GB DDR-3 1600
60GB Agility 3
2x160GB WD Caviar Blue in RAID-0
S/W
6GB RAM Drive (using primo, so it doesn't use this much ram all the time.)
SSD:
1GB RAM Cache
4kB cluster size
LRU Algorithm
Deferred Writing with 3s latency
RAID-O HDD
1GB RAM Cache
128kB Cluster size
LRU algorithm
Deferred Writing with 10s latency.
Normally, I see about a 1-2% read hit rate and a 50-110% deferred write rate on my HDD's, and I wasn't sure in what situations the read hit rate really shines. My HDD cache was the more important one to me, due to its wicked slow seek times compared to SSD and RAM. I wanted a buffer to help it deal with small files.
As I understand it, deferred writing is about like filling a balloon with water with a hole at the bottom. In inflates to a steady-state and then the output is a few seconds behind the input, but much more stable.
But in the case of reading, it seems like it's trying to "suck" data from a vacuum. The data has to be called in the first place, at the normal HDD rate, but it seems unlikely it would use the same data again unless it's the OS. (like my SSD)
So in what real-world situations could I really see the read cache being utilized? (Currently ~50MB free on the SSD and 500-600MB free on the RAID.)
Can I improve it much?
H/W
16GB DDR-3 1600
60GB Agility 3
2x160GB WD Caviar Blue in RAID-0
S/W
6GB RAM Drive (using primo, so it doesn't use this much ram all the time.)
SSD:
1GB RAM Cache
4kB cluster size
LRU Algorithm
Deferred Writing with 3s latency
RAID-O HDD
1GB RAM Cache
128kB Cluster size
LRU algorithm
Deferred Writing with 10s latency.
Normally, I see about a 1-2% read hit rate and a 50-110% deferred write rate on my HDD's, and I wasn't sure in what situations the read hit rate really shines. My HDD cache was the more important one to me, due to its wicked slow seek times compared to SSD and RAM. I wanted a buffer to help it deal with small files.
As I understand it, deferred writing is about like filling a balloon with water with a hole at the bottom. In inflates to a steady-state and then the output is a few seconds behind the input, but much more stable.
But in the case of reading, it seems like it's trying to "suck" data from a vacuum. The data has to be called in the first place, at the normal HDD rate, but it seems unlikely it would use the same data again unless it's the OS. (like my SSD)
So in what real-world situations could I really see the read cache being utilized? (Currently ~50MB free on the SSD and 500-600MB free on the RAID.)
Can I improve it much?