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From: Rich <rich@example.invalid>
Newsgroups: comp.os.linux.misc
Subject: Re: News : ARM Trying to Buy AmperComputing
Date: Tue, 21 Jan 2025 19:56:36 -0000 (UTC)
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D <nospam@example.net> wrote:
> [-- text/plain, encoding 8bit, charset: utf-8, 94 lines --]
> 
> 
> 
> On Mon, 20 Jan 2025, 186282@ud0s4.net wrote:
> 
>> On 1/20/25 3:53 PM, D wrote:
>>> 
>>> 
>>> On Mon, 20 Jan 2025, The Natural Philosopher wrote:
>>> 
>>>> On 20/01/2025 09:30, D wrote:
>>>>>> 
>>>>>>  The Pi hat or OMV ?
>>>>> 
>>>>> The pi, with directly connected spinning disks. Does the hat have its own 
>>>>> extra power supply?
>>>> 
>>>> I've managed to get a P4 I think to run one spinning rust disk without 
>>>> extra power.
>>>> Strictly it depends on the disk.
>>>> The pi hat for 5 drives has an external 60W PSU
>>> 
>>> Ahh, if it has an external PSU then there is no problem. Ideally, if the pi 
>>> hat for 5 drives is intended to accomodate 5 spinning drives, it would be 
>>> nice if it did so at full speeds.
>>
>>
>>  One review said the WRITEs were a little pokey,
>>  but not TOO bad. READs were apparently snappy.
>>
>>  This is OK ... most stuff on HDDs is "write once /
>>  read more often".
> 
> Hmm, do you have a link? What does "a little pokey" mean in terms of 
> writes? If it is only performance and latency related, then it is ok, 
> since the software will take care of a lot of that for me.

The nymshift troll was likely referring to two possibilities:

1) SMR mechanical drives
2) SSD's

In both cases, writes have to be done in what amounnts to a "two step 
process".

For SMR drives, because the magnetic tracks physically overlap, writes 
get queued to a non SMR area, and then get "moved" to the actual disk 
sectors as a bigger batch to maintain the proper "overlap" of the 
magnetic tracks.

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.