[plug] musing on HDD types

[William Kenworthy]

On 26/4/21 4:40 pm, Brad Campbell wrote:
> On 26/4/21 1:38 pm, William Kenworthy wrote:
>>
>> On 26/4/21 1:25 pm, Brad Campbell wrote:
>>> On 24/4/21 10:31 pm, Benjamin wrote:
>>>> don't go surveillance.
>>>
>>> Why not?
>>>
>> They are mostly CMR and relatively slow rpm but are optimised for
>> writing streaming data with little read optimisation - very specific
>> workload that is not suited to a chunkservers requirements (64Mb chunks
>> requiring multiple read random access after writing once.
>
> Surveillance systems do not present a nice neat "streaming write",
> "read rarely" load. They hammer the disks in both read and write
> scenarios, and operators do not like to be kept waiting while the
> system waits for a chunk of data. Even the consumer grade Chinese DVRs
> are increasingly random after the first couple of passes through the
> drive as footage is aged out.
>
> The only disadvantage to surveillance drives is they tend to have
> their power-saving patched out.
>
> Brad

Thats different to my readings and experience on the systems I have
seen  in various workplaces I have been - they mostly just wrote to disk
and were only ever read when archiving or the more rare examining
footage to identify theft or the like.  I never got into the tech side
of them, just a couple of times I was asked to examine a few
frames/images from them.

BillK