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From "Lu Ming" <>
Subject Re: Cassandra on flash storage
Date Wed, 09 Jun 2010 09:41:03 GMT
For hard disk drives, the random IOPS numbers are primarily dependent on the 
storage device's random seek time.
7200RPM SATA drives - ~90 IOPS[citation needed]
10kRPM Serial Attached SCSI drives - ~ 140 IOPS[citation needed]
15kRPM Serial Attached SCSI drives - ~180 IOPS[citation needed]
Intel X25-M (MLC; As of March 2010[update]) - ~8,600 IOPS (Intel's data 
sheet says 8,600 write, 35,000 read IOPS)

Random read throughput mainly depends on IOPS number per hard disk.
That's to say, if your cassandra node have only one hard disk with 200 IOPS 
per second and total rows of this node is far more than 1000,000,000, you 
can not read more than 200 different "random" rows per second in one disk 
cassadra node when no row-cache.

SSD has high IOPS, So it can highly improve the random read performance.

From: "Jonathan Ellis" <>
Sent: Tuesday, June 08, 2010 10:16 PM
To: <>
Subject: Re: Cassandra on flash storage

> cassandra is designed to do less random i/o than b-tree based systems
> like tokyo cabinet.  ssds are not as useful for most workloads.
> On Mon, Jun 7, 2010 at 8:37 AM, Héctor Izquierdo <> 
> wrote:
>> Hi everyone.
>> I wanted to know if anybody has had any experience with cassandra on 
>> flash
>> storage. At work we have a cluster of 6 machines running Tokyotyrant on
>> flash-io drives (320GB) each, but performance is not what we expected, 
>> and
>> we'are having some issues with replication and availability. It's also 
>> hard
>> to manage, and adding/removing nodes is pure hell.
>> We can't afford test hardware with flash storage right now, so could
>> somebody share his experience?
>> Thank you very much
>> Héctor Izquierdo
> -- 
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support

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