Comments on: Flash isn’t living up to the hype http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/ Data storage info & analysis Fri, 21 Nov 2008 20:39:51 +0000 http://wordpress.org/?v=2.6.3 By: Fazal Majid http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-131011 Fazal Majid Mon, 08 Oct 2007 06:19:13 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-131011 Amdahl's law. If disk access accounts for 40% of application execution time, a 100% improvement in disk access time will only lead to a 20% improvement in overall application performance. There is a law of diminishing returns and it is always important to build a balanced system. SSDs make the most sense for specific hot spots like Oracle redo logs. Of course, treating flash like disk and having the potential I/O throughput bottlenecked by slow and latency-inducing SATA or SAS interfaces does not help. Amdahl’s law. If disk access accounts for 40% of application execution time, a 100% improvement in disk access time will only lead to a 20% improvement in overall application performance. There is a law of diminishing returns and it is always important to build a balanced system. SSDs make the most sense for specific hot spots like Oracle redo logs.

Of course, treating flash like disk and having the potential I/O throughput bottlenecked by slow and latency-inducing SATA or SAS interfaces does not help.

]]> By: Robin Harris http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-122042 Robin Harris Sun, 16 Sep 2007 18:36:56 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-122042 Anon, I don't think you can be sure of *anything* with Windows. However, memory leaks are a known problem. Driver and BIOS problems wouldn't surprise me either. Thanks for relaying your experience. Robin Anon,

I don’t think you can be sure of *anything* with Windows. However, memory leaks are a known problem. Driver and BIOS problems wouldn’t surprise me either. Thanks for relaying your experience.

Robin

]]> By: Anon http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-119512 Anon Fri, 14 Sep 2007 19:16:17 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-119512 I know you mention memory leaks twice in reference to XP suspend issues but are you sure it is memory leaks that are to blame? I've heard (and only have limited proof by watching machines with the same image but differing hardware) that repeated suspension failure is often due to driver bugs and hardware/BIOS faults... I know you mention memory leaks twice in reference to XP suspend issues but are you sure it is memory leaks that are to blame? I’ve heard (and only have limited proof by watching machines with the same image but differing hardware) that repeated suspension failure is often due to driver bugs and hardware/BIOS faults…

]]> By: Robin Harris http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-119466 Robin Harris Fri, 14 Sep 2007 18:07:23 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-119466 Jonathan, thanks for the comment - it made me realize the chart wasn't as clear as it should be. I hope the update helps. Yeroc, flash is very energy efficient. The numbers from AnandTech were on the order of almost zero at rest and 0.55 W when writing. The Seagate was about 5x that when writing. In the context of a laptop though, where disks account for about 15-20% of the power load, a flash drive will turn a 3 hour laptop into a 3.5 hour laptop. Good, but how many people will pay $500-$1000 for 30 minutes more battery life? As part of an integrated design using several power-saving techniques an SSD makes sense. As an upgrade not so much. Graeme, interesting numbers. The AnandTech tests I referred to were done on Vista and they did better, so it isn't clear what the issue might be. I haven't played with Vista myself, but my big concern is memory leaks - a long time Windows problem - making the faster startups from standby and hibernate modes moot since the system will crash as it attempts to exit standby. Robin Jonathan, thanks for the comment - it made me realize the chart wasn’t as clear as it should be. I hope the update helps.

Yeroc, flash is very energy efficient. The numbers from AnandTech were on the order of almost zero at rest and 0.55 W when writing. The Seagate was about 5x that when writing.

In the context of a laptop though, where disks account for about 15-20% of the power load, a flash drive will turn a 3 hour laptop into a 3.5 hour laptop. Good, but how many people will pay $500-$1000 for 30 minutes more battery life? As part of an integrated design using several power-saving techniques an SSD makes sense. As an upgrade not so much.

Graeme, interesting numbers. The AnandTech tests I referred to were done on Vista and they did better, so it isn’t clear what the issue might be. I haven’t played with Vista myself, but my big concern is memory leaks - a long time Windows problem - making the faster startups from standby and hibernate modes moot since the system will crash as it attempts to exit standby.

Robin

]]> By: Jonathan Ragan-Kelley http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-117392 Jonathan Ragan-Kelley Thu, 13 Sep 2007 00:54:40 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-117392 Am I wrong to note that the "flash vs. disk" comparison graph you posted is comparing the pure-flash SSD to a flash-hybrid Samsung drive, not the conventional Seagate drive? (I believe the macroscopic numbers about marginally better normalized overall performance, and the article as a whole matches your analysis, but the key on the plot you included seems odd given that you're drawing a flash vs. conventional disk comparison here, and not comparing flash to a conventional disk.) Am I wrong to note that the “flash vs. disk” comparison graph you posted is comparing the pure-flash SSD to a flash-hybrid Samsung drive, not the conventional Seagate drive? (I believe the macroscopic numbers about marginally better normalized overall performance, and the article as a whole matches your analysis, but the key on the plot you included seems odd given that you’re drawing a flash vs. conventional disk comparison here, and not comparing flash to a conventional disk.)

]]> By: Yeroc http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-117095 Yeroc Wed, 12 Sep 2007 18:21:50 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-117095 It would be interesting to add energy efficiency to the equation as well. How well do the Flash drives hold up in that respect? I assume very well...but I don't really know how much power it takes to write data to falsh... It would be interesting to add energy efficiency to the equation as well. How well do the Flash drives hold up in that respect? I assume very well…but I don’t really know how much power it takes to write data to falsh…

]]> By: Graeme http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-116974 Graeme Wed, 12 Sep 2007 15:39:55 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-116974 I've found in my informal testing that Vista has massive I/O problems. A computer setup that can exceed 20 MB / sec on a stock SATA drive in standard large file copies under XP SP2, and 25 MB / sec in Linux, is only able to push around 9.5 MB / sec on Vista. I've disabled all of Vista's "smart" features, such as their load-ahead stuff and their indexing, but it doesn't change the performance numbers. As well, my primary test system sometimes locks I/O, in that open applications stay running, but it fails to do any disk I/O for around 2-4 minutes, before recovering in a flurry of queued I/O requests that lasts almost as long as the lock period. What I suspect in reference to the Anandtech testing is that there is larger performance gains to be had from flash drives, but massive bugs in Vista's I/O are failing to show them. I'd be interested in seeing performance comparisons from Linux, ZFS on Solaris, or even XP SP2, as I think they'd be a lot more valid. I’ve found in my informal testing that Vista has massive I/O problems. A computer setup that can exceed 20 MB / sec on a stock SATA drive in standard large file copies under XP SP2, and 25 MB / sec in Linux, is only able to push around 9.5 MB / sec on Vista. I’ve disabled all of Vista’s “smart” features, such as their load-ahead stuff and their indexing, but it doesn’t change the performance numbers. As well, my primary test system sometimes locks I/O, in that open applications stay running, but it fails to do any disk I/O for around 2-4 minutes, before recovering in a flurry of queued I/O requests that lasts almost as long as the lock period.

What I suspect in reference to the Anandtech testing is that there is larger performance gains to be had from flash drives, but massive bugs in Vista’s I/O are failing to show them. I’d be interested in seeing performance comparisons from Linux, ZFS on Solaris, or even XP SP2, as I think they’d be a lot more valid.

]]> By: hoberion http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-116923 hoberion Wed, 12 Sep 2007 14:35:44 +0000 http://storagemojo.com/2007/09/12/flash-isnt-living-up-to-the-hype/#comment-116923 try zfs? try zfs?

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