Endurance Testing the Samsung 840 EVO SSD

How long will the Samsung 840 EVO last?
When will it run out of write cycles?

Samsung has not given any official P/E count or TBW rating for the EVO series. On their global site they claim 10GB writes per day will make the 120GB version last for 28 years. This roughly translates to 100 TBW. Let's wear it out and see if it dies gracefully...

Samsung 840 EVO SSD Endurance Test

Preliminary Data - Test is Running
TiB Written
Estimated Cycles
Hours Online
Endurance Cycles are estimated as NAND/Host writes reported by S.M.A.R.T. divided by the SSD capacity.
TiB Written is pure user data. Hours Online include read/write/smart/overhead.

Average speed  Last two reported
Read Speed132 MB/s82 MB/s92 MB/s
Write Speed  23 MB/s25 MB/s19 MB/s

Please note that this unit is heavily stressed and in steady state most of the time.
Started at Sep 3. Last update Nov 2 06:59.

Samsung 19nm TLC NAND

S.M.A.R.T. Data Logging

The health of the Samsung 840 EVO is monitored by reading the SMART data throughout the test.

The MWI increase at 2.5TB is a result from changing the random write pattern from a evenly distributed model to a more chaotic approach. No change to the reported NAND writes. My guess would be that this is the effect of aggressive TLC wear leveling.

The write amplification is steady at 2x. Based on this graph, the EVO does not show any signs of compressing data when writing to NAND - or at least not reporting it.

The Samsung 840 EVO is in steady state most of the time during this test. Alternating between random and sequential writes every 16GiB does not allow it to recover noticably. The average write speed is the average of all write operations (50% sequential and 50% random). Block sizes are distributed evenly between 4k and 128k. Incompressible and non repeatable random data is used. Drive firmware is EXT0AB0Q.

Write Performance and RAID

This is clearly a consumer level SSD ment for light loads. To be fair this is also what Samsung communicates. I would strongly advice against using the Samsung 840 EVO in any RAID setup with durable write performance in mind.

TRIM is necessary to keep this SSD in good shape. This rules out most RAID setups, which prevents the use of TRIM. The test average write speed is very indicative. It will most likely settle at just above 20MB/s. Please remember that these numbers are for high load steady state. Initially this drive performed well over 200MB/s, this will most likely be the typical speed when kept in good shape using TRIM. Burst speeds will be higher.

I moved the SSD to a different test test server just to rule out any hardware incompatibilites (did this at 10.78TiBW). The drive was plugged in but left idle for 30 minutes before I could resume the test on the new server. Got appx. 15 seconds of write speed above 100MB/s before it dropped back down again.

On the positive side we have the high read speeds. Sure, it should be faster than the smaller units as it's twice their size. So please read and compare reviews of similar sized and priced units before drawing any conclusions.

Device information

Device Model:     Samsung SSD 840 EVO 120GB
Serial Number:    S1D5NEA#######T
LU WWN Device Id: 5 002538 8######6e
Firmware Version: EXT0AB0Q
User Capacity:    120,034,123,776 bytes [120 GB]
Sector Size:      512 bytes logical/physical

Reviews of the Samsung 840 EVO

Samsung SSD 840 EVO Review
"120GB, 250GB, 500GB, 750GB & 1TB Models Tested."   Anand Lal Shimpi, AnandTechRead it »

Feedback and Comments on Samsung 840 EVO

Is this really normal?

No. The tests preformed here must not be confused with normal use. They are designed to stress SSDs and simulate a really busy environment.
Normal workstation use would be more like 10-20GB written daily.

TRIM and SSD Endurance in RAID Arrays »

Failed SSD = Bad SSD?

Don't worry. All drives tested here are perfectly suited for normal use. No doubt.
This SSD test is more about how they fail.
We want to see warnings of imminent failure, not just a sudden death.

How About Data Retention?

The term Data Retention refers to how long the data preserved is if the SSD is left unpowered. The plan is to test data retention once a SSD reaches extreme TBW. Please be carefull with your data and with SSDs that have outlived their specifications.

Why Test Smaller SSDs?

They use fewer NAND circuits and will wear out faster. Once we know the write endurance of these units, it'll be easy to estimate the equivalent numbers for the larger units.