Skip site navigation (1) Skip section navigation (2)

Re: Testing Sandforce SSD

From: Greg Smith <greg(at)2ndquadrant(dot)com>
To: Matthew Wakeling <matthew(at)flymine(dot)org>
Cc: Yeb Havinga <yebhavinga(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Testing Sandforce SSD
Date: 2010-07-26 15:28:02
Message-ID: 4C4DA982.5090308@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-performance
Matthew Wakeling wrote:
> Does your latency graph really have milliseconds as the y axis? If so, 
> this device is really slow - some requests have a latency of more than 
> a second!

Have you tried that yourself?  If you generate one of those with 
standard hard drives and a BBWC under Linux, I expect you'll discover 
those latencies to be >5 seconds long.  I recently saw >100 *seconds* 
running a large pgbench test due to latency flushing things to disk, on 
a system with 72GB of RAM.  Takes a long time to flush >3GB of random 
I/O out to disk when the kernel will happily cache that many writes 
until checkpoint time.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com   www.2ndQuadrant.us


In response to

Responses

pgsql-performance by date

Next:From: Greg SmithDate: 2010-07-26 15:34:00
Subject: Re: Testing Sandforce SSD
Previous:From: Yeb HavingaDate: 2010-07-26 10:29:42
Subject: Re: Testing Sandforce SSD

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group