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Volker Armin Hemmann writes: |
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> Am Sonntag, 26. August 2012, 13:41:09 schrieb Alex Schuster: |
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>> Frank Steinmetzger writes: |
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>>> Unless the filesystem knows this and starts bigger files at those 512 k |
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>>> boundaries (so really only one erase cycle is needed for files <=512 k), |
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>>> isn't this fairly superfluous? |
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>> |
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>> Yes, I think it is. When you search for SSD alignment, you read about |
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>> this alignment all the time, even on the German Wikipedia, and many |
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>> resources say that this can have a big impact on performance. But I |
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>> could not find a real explanation at all. |
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>> |
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>> Besides that, it's not so easy to do the alignment, at least when using |
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>> LVM. I read that LVM adds 192K header information, so even if you align |
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>> the partition start to an erasable block size of 512K, the actual |
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>> content is not aligned. See [*] for information how to overcome this. |
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>> That is, if you believe the alignment to erasable blocks is important, |
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>> personally I do not know what to think now. It wouldn't hurt, so why not |
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>> apply it, but it seems like snake oil to me now. |
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>> |
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>> Wonko |
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>> |
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>> http://tytso.livejournal.com/2009/02/20/ |
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> |
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> because erasing is slow. You can not overwrite data on a ssd. you have to |
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> erase first, then reprogramm. Also, erasing shortens lifetime. |
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Yes, I know that. But why exactly does it help to align a partition to |
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the erasable block size? I don't get it. Why isn't it sufficient to |
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align to the usual 4K block size, so that a block never spans over two |
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erasable blocks? |
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Wonko |
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