Opet corak odgovor, ali ipak sam nasao dalje ono sto me zanimalo.
Covjek se isto pita sto i ja:
The limited writings and capacity\price of the SSD are known drawbacks as the sensitivity to shocks of the HDD.
The hybrid SSHD (standard HDD+SSD cache) have a classic HD combined with a small SSD used as cache and managed by the firmware of the SSHD.
Now I want to know what happens when the SSD cache reaches the writing limit quote for all the cells, the two possible alternatives are:
a) simply the firmware stop to use the SSD caching and the SSHD becomes a standard HDD
b) the SSHD becomes unusable
What is the right answer? (The b alternative would make the SSHD choice, the less durable alternative and the worst choice ever for a server.)
I have searched reliable sources about this, but I haven't found anything.
The mechanical problems of HDD are very rare if they they are not subjected to shocks during the read\write operations, in standard condition the MTF range between 1 million to 1.5 million hours for a modern HDD. In the SSD, particularly SSD TLC, wearing is a problem, MLC typical maximum PE-cycle-per-block numbers range from 1500 to 10,000 (5000 mostly). Reach 5000 cycles is relatively easy if the storage is used intensively (especially in server use). So It's really important the SSD cache durability, and in addition must be considered also that cache-SSD sectors in SSHD are used even most intensively of a standard SSD that can distribute the wearing on a larger space.
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Odgovor slijedi:
For SSHD users, we do worry about what happen when the SSD Cache wear out.
Toshiba does provide official information on their
SSHD FAQ.
I have heard that NAND flash can wear out over time. What happens if the NAND component in the Toshiba SSHD reaches its endurance limit? Will data be lost?
Should the user exceed the endurance limit of the NAND flash, the Toshiba SSHD will continue functioning as a conventional HDD. However, before the NAND flash component reaches the endurance limits, its performance will gradually decline. Due to Toshiba’s NAND flash caching algorithms and data protection mechanisms, Toshiba does not expect an increased risk of data loss resulting from aging of the NAND flash on the Toshiba SSHD during the expected lifetime of a PC.
But I cannot find any similar information from
Seagate, I have no proof to know it’s the same to Seagate SSHD.
SSD cache in SSHD compromises the lifecycle compared to standard HDD? on
superuser provides a good discussion on this topic.
My conclusion: before the SSD cache wear out, there will be more and more damaged chips in SSD which means the available SSD cache is becoming smaller and smaller. User shall notice that the performance is decline slowly without any warning from
S.M.A.R.T. .
Linkovi na clanke:
http://superuser.com/questions/58116...o-standard-hdd
https://amigotechnotes.wordpress.com...ache-wear-out/