How is endurance of SSDs measured and what is the impact of write amplifications?
I have an Intel SSD Pro 2500 Series 480 GB drive. Recently I got a notification that my drive is failing. I was surprised because it is less than 2 years old. I used the Intel SSD utility to check the SMART status and see results shown in screen shot.
A few things stand out:
E8 available reserved space is low. This is probably why I got a notification saying the disk was failing.
Total Host write is about 8.9 TB. That's a lot, but not an unreasonable amount.
Total NAND writes is about 202 TB. That's a lot more and I think it's close to the endurance of the drive.
I looked at the drive manual and the specs say:
Minimum Useful Life/Endurance Rating
The SSD will have a minimum of five years of useful life under typical client workloads of up to 20 GB of host writes per day.
By my calculation that means the drive support 20 GB * 365 day/year * 5 years = 36.5 TB of writes.
So my 8.9 TB of host writes is well under the 36.5 TB threshold, but the 202 TB of NAND writes is well above that threshold.
My first question is: Are drive endurance figures based on host writes or NAND writes?
I assume it is NAND writes since that's what the drive is actually doing, but if anyone has more concrete answer that would be useful.
My second question is: What are reasonable values for write amplification on Windows client workloads and is my 22.7 times write amplification high? If so how can I reduce it?
I checked to see if trim is enabled and I think it is:
C:\WINDOWS\system32>fsutil behavior query DisableDeleteNotify NTFS DisableDeleteNotify = 0
I found one white paper that indicates this is a normal level of write amplification:
The write amplification factor on many consumer SSDs is anywhere from 15 to 20.
But I've also seen other things that indicate write amplification should be closer to 1. So that's the reason I'm asking here to see if anyone has useful insight.
Addendum: BitLocker Question
In the process of writing this question I found a review of my drive. Part of the review says:
The TRIM issue has not changed. Again it is not a problem unless you use software encryption because otherwise there will always be compressible data, but given the Opal and eDrive support in the Pro 2500, I do not see why anyone would opt for the Pro 2500 if the plan is to utilize software encryption.
I don't know exactly what the TRIM issue is, but my drive does have encryption enabled with Bitlocker (part of IT policies). I searched to see how to check if the drive uses built-in encryption and it seems that my drive is not using hardware encryption. Running the command
manage-bde.exe -status c: shows:
C:\WINDOWS\system32>manage-bde.exe -status c: BitLocker Drive Encryption: Configuration Tool version 10.0.14393 Copyright (C) 2013 Microsoft Corporation. All rights reserved. Volume C: [Windows] [OS Volume] Size: 445.05 GB BitLocker Version: 2.0 Conversion Status: Fully Encrypted Percentage Encrypted: 100.0% Encryption Method: AES 256 Protection Status: Protection On Lock Status: Unlocked Identification Field: Unknown Key Protectors: TPM And PIN Numerical Password
My guess now is that the Sandforce controller is not working well with uncompressible encrypted data. Still if anyone has more detailed answers to my questions they are appreciated.