03-28-2018 10:14 AM - edited 03-29-2018 08:06 AM
I think 25% OP (Over-Provisioning) is the sweet spot between data integrity, space and speed. Which of the following is the best way to set OP to 25%?
- Open CSE (Crucial Storage Executive) and set OP to 25%. (Is this the same as simply keeping 25% logical space unallocated?)
- Set the HPA (Host Protected Area) to 25% and, besides that, do nothing.
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04-02-2018 09:25 AM
simplest way is to just leave unpartitioned space but either method will of course work. I leave unpartitioned space rather than use the executive program as a linux user. while the actual user space of my MX500 is 500GB I've reduced that to 480GB usable space via partitioning. what size drive are you talking about here? the recommendations from crucial are between 5-10% for all their SSD according to the knowledgebase articles.
I set aside 25GB for my MX300 525GB and treated it as a 500GB drive when partitioning.
04-02-2018 01:32 PM - edited 04-03-2018 02:46 PM
We are talking about a 512GB SSD. To maintain data integrity i must sacrifice some space for the so called parity bits. 12.5% OP means 1 parity bit for every 7 bits data. (Please correct me if i'm wrong.)
The funny thing is, hdparm says: HPA disabled. I can allocate all the physical space to Linux or Windows. Even the Crucial Storage Executive application says: 0% OP.
My guess would be that if i set the HPA to 12.5% or 25% then the controller (onboard the SSD) knows for sure how much space will not be allocated and the controller can adjust the error correcting code to that space.
04-02-2018 06:11 PM - edited 04-02-2018 06:24 PM
I had the same zero overprovisioning value for my 525GB MX300 but not the new MX500. it may still show as zero (I hadn't checked prior to partitioning) but there was near enough 12GB reserved space on the 500GB MX500 already as it equalled the same free GiB value in the Partition Manager as a 500GB drive would when unpartitioned. I had windows installed on the MX300 as well originally and recall Crucial Storage Executive reporting zero percent overprovisioning too. I think you are correct about parity BUT contact crucial to find out the applicable ratio for your SSD model before proceeding any further. the document gives values specific to a particular pci-e model.
That RAIN document makes for interesting reading, what's concerning is the example shown actually ends up reducing the user space by a massive 162GB. If it's not the only drive in the system it wouldn't matter so much but otherwise you really have to question the actual value of RAIN if you already have a regular backup regime.