On 2010-06-24 15:45, Janning Vygen wrote:
On Thursday 24 June 2010 15:16:05 Janning wrote:
On Thursday 24 June 2010 14:53:57 Matthew Wakeling wrote:
On Thu, 24 Jun 2010, Janning wrote:
We have a 12 GB RAM machine with intel i7-975 and using
3 disks "Seagate Barracuda 7200.11, ST31500341AS (1.5 TB)"
For each drive, you will be able to read/write approximately 8kB /
0.0085s, giving 941kB per second. If you have multiple processes all
doing random access, then you may be able to utilise both discs and get
double that.
So with your calculation I have a maximum of 2MB/s random access. So i
really need to upgrade my disk configuration!
i was looking at tomshardware.com and the fastest disk is
Maxtor Atlas 15K II * 8K147S0,SAS,147 GB, 16 MB Cache,15000 rpm
with 5.5 ms random access time.
So even if i switch to those disks i can only reach a perfomace gain of 1.5,
right?
To achieve a better disk performance by factor of ten, i need a raid-10 setup
with 12 disks (so i have 6 raid-1 bundles). Or are there other factors with
high end disks?
Well. On the write-side, you can add in a Raid controller with Battery
backed
write cache to not make the writes directly hit disk. This improves
the amount of writing you can do.
On the read-side you can add more memory to your server so a significant
part of your most active dataset is cached in memory.
It depends on the actual sizes and workload what gives the most benefit
for you.
--
Jesper
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