Comments on: Bcache Testing: Throughput http://www.linux-mag.com/id/7843/ Open Source, Open Standards Sat, 05 Oct 2013 13:48:18 +0000 hourly 1 http://wordpress.org/?v=3.1 By: kkpmvukauqc http://www.linux-mag.com/id/7843/#comment-142687 kkpmvukauqc Tue, 07 Feb 2012 08:22:12 +0000 http://www.linux-mag.com/id/7843/#comment-142687 VVs6oL <a href="http://meksekmlqbkj.com/" rel="nofollow">meksekmlqbkj</a> VVs6oL meksekmlqbkj

]]> By: Yui http://www.linux-mag.com/id/7843/#comment-142643 Yui Tue, 07 Feb 2012 07:14:42 +0000 http://www.linux-mag.com/id/7843/#comment-142643 Try this… (copied from my wobsehts wiki, i was having a similar problem, this may solve it…)Blank PagesIf you have “blank pages” in WordPress with wp-cache turned on after you upgrade to PHP 5.1.2 – there is simple fix to solve the problem:-<ol><li>Open /wp-content/plugins/wp-cache/wp-cache-phase2.php file* in your favourite text editor, where is the domain that you’re having troubles with EG: dreamhost.com/wp-content/plugins/wp-cache/wp-cache-phase2.php</li><li>Alternatively if that file is not in that location for some reason you can issue this command to find it from the directory: find . -name wp-cache-phase2.php</li><li>Find out wp_cache_ob_end function</li><li>then inside that function find the line with: ob_end_clean(); (it should be line 219 or about)</li><li>and finally replace that line with: ob_end_flush();</li></ol> Try this… (copied from my wobsehts wiki, i was having a similar problem, this may solve it…)Blank PagesIf you have “blank pages” in WordPress with wp-cache turned on after you upgrade to PHP 5.1.2 – there is simple fix to solve the problem:-<ol><li>Open /wp-content/plugins/wp-cache/wp-cache-phase2.php file* in your favourite text editor, where is the domain that you’re having troubles with EG: dreamhost.com/wp-content/plugins/wp-cache/wp-cache-phase2.php</li><li>Alternatively if that file is not in that location for some reason you can issue this command to find it from the directory: find . -name wp-cache-phase2.php</li><li>Find out wp_cache_ob_end function</li><li>then inside that function find the line with: ob_end_clean(); (it should be line 219 or about)</li><li>and finally replace that line with: ob_end_flush();</li></ol>

]]> By: paul.dorman http://www.linux-mag.com/id/7843/#comment-8633 paul.dorman Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8633 <p>Hi Jeff, thanks for the thorough tests. I've been seriously considering a 50-70GB SSD as a second drive in my laptop to reap the potential benefits of BCache and similar projects.</p> <p>As a BTRFS user I am very interested in the recent BTRFS patches for hot data relocation (http://lwn.net/Articles/400029/). It will certainly be interesting to see how effective these are at increasing performance for a relatively low outlay.</p> <p>Irrespective of which approach gives the best result, I think that tiered storage using complementary SSDs will be a big win for everyone - particularly Linux users, and especially those with high-performance laptops that suffer most significantly from the disk I/O bottleneck.</p> <p>Regards,<br /> Paul </p> Hi Jeff, thanks for the thorough tests. I’ve been seriously considering a 50-70GB SSD as a second drive in my laptop to reap the potential benefits of BCache and similar projects.

As a BTRFS user I am very interested in the recent BTRFS patches for hot data relocation (http://lwn.net/Articles/400029/). It will certainly be interesting to see how effective these are at increasing performance for a relatively low outlay.

Irrespective of which approach gives the best result, I think that tiered storage using complementary SSDs will be a big win for everyone – particularly Linux users, and especially those with high-performance laptops that suffer most significantly from the disk I/O bottleneck.

Regards,
Paul

]]> By: laytonjb http://www.linux-mag.com/id/7843/#comment-8634 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8634 <p>@Paul,</p> <p>I agree with you. While Bcache and flashcache are still in their infancy the concept of using SSD's for caching is a good one. I can imagine taking several inexpensive SSD's, creating a RAID-0 and using that to cache a RAID-6 or something similar.</p> <p>I too am watching the btrfs patches. Next concept. In fact I think it's good enough that the authors can make it generic and put it in the vfs (at least I hope they do).</p> <p>Thanks for the post!</p> <p>Jeff </p> @Paul,

I agree with you. While Bcache and flashcache are still in their infancy the concept of using SSD’s for caching is a good one. I can imagine taking several inexpensive SSD’s, creating a RAID-0 and using that to cache a RAID-6 or something similar.

I too am watching the btrfs patches. Next concept. In fact I think it’s good enough that the authors can make it generic and put it in the vfs (at least I hope they do).

Thanks for the post!

Jeff

]]> By: lkliu http://www.linux-mag.com/id/7843/#comment-8635 lkliu Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8635 <p>I believe the block size is too big for such test. When the block size >1MB, the disk gets a lot of benefit from the sequential read or write. In one words, I think this test underestimate the benefits of using ssd and bcahce to improve performance. </p> I believe the block size is too big for such test. When the block size >1MB, the disk gets a lot of benefit from the sequential read or write. In one words, I think this test underestimate the benefits of using ssd and bcahce to improve performance.

]]> By: bugmenot3 http://www.linux-mag.com/id/7843/#comment-8636 bugmenot3 Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8636 <p>In this blog:<br /> http://virtualgeek.typepad.com/virtual_geek/2010/05/emc-unified-storage-next-generation-efficiency-details.html<br /> benefits of "FAST Cache" feature of EMC disk-arrays is shown.<br /> "FAST Cache" uses Flash as second-level cache of traditiona disks and it seems that it gives good improvements. </p> In this blog:
http://virtualgeek.typepad.com/virtual_geek/2010/05/emc-unified-storage-next-generation-efficiency-details.html
benefits of “FAST Cache” feature of EMC disk-arrays is shown.
“FAST Cache” uses Flash as second-level cache of traditiona disks and it seems that it gives good improvements.

]]> By: dbbd http://www.linux-mag.com/id/7843/#comment-8637 dbbd Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8637 <p>The results presented in the article are very poor. I thought bcache makes a lot of sense, but the results demonstrate it is far from ready for prime time. </p> The results presented in the article are very poor. I thought bcache makes a lot of sense, but the results demonstrate it is far from ready for prime time.

]]> By: laytonjb http://www.linux-mag.com/id/7843/#comment-8638 laytonjb Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8638 <p>@dbbd,</p> <p>You are correct - bcache isn't ready for production. Even the author admits this. But I think this a time where we can influence bcache and ask for changes. For example, Kent, the author, knows that bcache doesn't have a writethrough capability now and that impacts performance as I presented.</p> <p>Great time to influence possible kernel patches.</p> <p>Jeff </p> @dbbd,

You are correct – bcache isn’t ready for production. Even the author admits this. But I think this a time where we can influence bcache and ask for changes. For example, Kent, the author, knows that bcache doesn’t have a writethrough capability now and that impacts performance as I presented.

Great time to influence possible kernel patches.

Jeff

]]> By: homarne http://www.linux-mag.com/id/7843/#comment-8639 homarne Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8639 <p>Jeff,</p> <p>I've read through the article a couple of times and can't figure one thing out.</p> <p>If the working set of the test you ran was 16GB, and the SSD was 64GB, then the entire working set should have fit in the SSD cache, and the cache performance should have been very close to the SSD performance (unless bcache is VERY inefficient).</p> <p>What the SSD cache size in fact set to a smaller size than the working set? If so I can't figure out where you mention this in the article.</p> <p>Thanks - Tom </p> Jeff,

I’ve read through the article a couple of times and can’t figure one thing out.

If the working set of the test you ran was 16GB, and the SSD was 64GB, then the entire working set should have fit in the SSD cache, and the cache performance should have been very close to the SSD performance (unless bcache is VERY inefficient).

What the SSD cache size in fact set to a smaller size than the working set? If so I can’t figure out where you mention this in the article.

Thanks – Tom

]]> By: ihatesigningup http://www.linux-mag.com/id/7843/#comment-8640 ihatesigningup Wed, 30 Nov -0001 00:00:00 +0000 http://www.linux-mag.com/id/7843/#comment-8640 <p>Jeff,</p> <p>Please consider benchmarking bcache and the other one I whose name I can't remember with an sql benchmark, or some sort of "real-world" benchmark.</p> <p>The reason I mention this is because, if you ran a busy Web site like facebook, and used bcache to speed up your database. I mean bcache was written to speed up this scenario, and I think bcache would really shine in this workload, because just like on a busy Web site there would be many more reads that writes, and many of those reads could stay in the SSD cache. </p> <p>Thanks,<br /> Dave. </p> Jeff,

Please consider benchmarking bcache and the other one I whose name I can’t remember with an sql benchmark, or some sort of “real-world” benchmark.

The reason I mention this is because, if you ran a busy Web site like facebook, and used bcache to speed up your database. I mean bcache was written to speed up this scenario, and I think bcache would really shine in this workload, because just like on a busy Web site there would be many more reads that writes, and many of those reads could stay in the SSD cache.

Thanks,
Dave.

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