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From: The Natural Philosopher <tnp@invalid.invalid>
Newsgroups: comp.os.linux.misc
Subject: Re: News : ARM Trying to Buy AmperComputing
Date: Wed, 22 Jan 2025 23:55:19 +0000
Organization: A little, after lunch
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On 22/01/2025 20:08, Rich wrote:
> The Natural Philosopher <tnp@invalid.invalid> wrote:
>> On 21/01/2025 19:56, Rich wrote:
>>> For SSD's, writes occur to an "erased" flash block (typically much
>>> larger than a "disk sector" size used by the host) and given enough
>>> writes over a short enough timeframe the SSD controller can run out of
>>> "pre-erased" blocks to use, and when that happens write speed slows
>>> down to the rate that can be done when a "block erase" has to occur
>>> before the actual writes can hit the media.  Note that this "block
>>> erase" can also invove moving any partially used data sectors out of
>>> the block into another block, creating a "write amplification"
>>> situation as well.
>>
>> One of the best ways to gain speed and longevity is to buy an SSD that
>> is way larger than you need. So it always has empty blocks available.
> 
> And hope it has a decent block layer that spreads the writes around so
> no one part of the flash is written to more than any other parts.
> 
That is pretty much standard practice these days Its called 'wear levelling'

>> And can do the block erases in background
> 
> Most SSD's do erases in the background, so that they can have empty
> blocks waiting to absorb writes.
> 
....Exactly...
> But stream a large enough set of writes at the drive, and you can (for
> some drives) use up the queue of background erased blocks and then you
> see your write speed drop by a good amount because the block erases are
> now also part of the "write path" for your data heading at the drive.

.....that was precisely the point I was making.


-- 
"If you don’t read the news paper, you are un-informed. If you read the 
news paper, you are mis-informed."

Mark Twain