> bloom filters can guess right sstables to be read with high
> probability < 0.1%. In reality even if you are using size based
> compaction and have about 300 sstables, reading is fast unless
> there is row fragmentation and you are reading entire row.
Right, that's it. Thanks!
Hi,
If the rows are updated by random keys, then most of the SSTables will have
overlapping
key ranges, right? Then for each read, Cassandra will go through all the
SSTables (or
one SSTable in each level for the leveled compaction strategy)? How to deal
with this
problem?
Thanks!
--
Author o
> It is not telling you to multiply your key size by 10-12, it is telling you to
> multiply the output of the nodetool cfstats reported "key cache size" by
> 10-12.
The "key cache size" reported is actually the number of keys in the key cache.
So,
it is the same thing as suggesting each key ta
Hi,
From the source code I can see that for each key, the hash (token), the key
itself (ByteBuffer) and the position (long. offset in the sstable) are stored
into the key cache. The hash is an MD5 hash, so it is 16 bytes. So, the total
size required is at least 16+size-of(key)+4 which is > 20 b
)
From: Peter Tillotson
To: "user@cassandra.apache.org" ; Kent Tong
Sent: Friday, December 16, 2011 1:45 AM
Subject: Re: performance reaching plateau while the hardware is still idle
May I suggest dstat, does cpu, memory, and io on one console
dstat -vn 3
S
Hi,
I am running a performance test for Cassandra 1.0.5. It can perform about 1500
business operation (one read+one write to the same row) per second. However,
the CPU is still 85% idle (as shown by vmstat) and the IO utilization is less
than a few percent (as shown by iostat). "nodetool tpstat
Hi,
I was wondering if two records with "adjacent" keys are stored near-by, or with
"adjacent" key hashes or neither?
Thanks!
Tong
Sent: Monday, November 21, 2011 5:22 AM
Subject: Re: read performance problem
There is something wrong with the system. Your benchmarks are way off. How are
you benchmarking? Are you using the stress lib included?
On Nov 19, 2011 8:58 PM, "Kent Tong" wrote:
Hi,
>
>
>
Hi,
On my computer with 2G RAM and a core 2 duo CPU E4600 @ 2.40GHz, I am testing
the
performance of Cassandra. The write performance is good: It can write a million
records
in 10 minutes. However, the query performance is poor and it takes 10 minutes
to read
10K records with sequential keys
