[Tfug] Small-ish (capacity + size) disk alternatives

[Bexley Hall]

Hi,

On 1/29/2013 5:30 PM, JD Rogers wrote:

[attrs elided]

>>>> SSD's would probably fail in short order due to the
>>>> inherent media life limitations (the read-write uses for
>>>> the disk involve lots of update cycles).
>>>
>>> Most SSD's publish the number of writes before they'd fail.  As you
>>> have the system running, you can probably figure out your daily amount
>>> of data being read/written to the disk, and then extrapolate how long
>>> an SSD would theoretically last.  Also, the larger the SSD, the larger
>>> the "spare" area, so they tend to last longer.
>>
>> Yes, it would be more economical to replace laptop drives every
>> couple of months than an SSD every year.<frown>   Or, maybe
>> look at some of the small form factor SCSI drives (*intended*
>> to run continuously -- unlike laptop drives).
>
> Seems like 32GB SSDs are less than $50 these days and since you don't
> need a lot of space, it sounds right. Can you reduce the reads and
> writes some using some clever scripting to minimize writes?

No.  The disk is used as "slow memory".  I.e., much cheaper than
putting 10's of GB of RAM in the system when it isn't accessed
all that frequently (or, its contents not needed all that *quickly*).

(10's of GB of faster-than-necessary RAM also have other ramifications)

E.g., decades ago (when RAM was $100/MB) swap on rotating media
was a *huge* way to leverage your capabilities (since disk was
two orders of magnitude cheaper!).  Sure, it was slower than
RAM but you could do a lot to *hide* that cost (intelligent
paging operations and scheduling disk i/o in the background
once true memory managed architectures were available).  And,
if you could *really* afford to wait, you spooled the data off
to *tape*!  <grin>

Nowadays, it's common to have 10's of GB of RAM in a box so you
don't see the advantages of disk as a "RAM alternative", as much.
Rather, you tend to regard disk more as "nonvolatile storage".
(Even the ROM and FLASH that are used are treated more as
"nonvolatile storage" -- often copied into system RAM instead of
XIP)

If you can trade one characteristic for another and end up ahead...

(Why doesn't your PC come with 100's of GB's of RAM?  Or, 1TB of
NAND FLASH on the motherboard to eliminate the need for the disk
drive?  etc.)