13 521
правка
Изменения
Нет описания правки
Supercaps are usually called «enhanced/advanced power loss protection» in the datasheets. This is a feature almost exclusively present only on «server-grade» SSDs (not even all of them). For example, Intel DC S4600 has supercaps and Intel DC S3100 doesn’t.
{{Note}} This is the main difference between server and desktop SSDs. The average user doesn’t need transactions, but the servers run DBMS’es, and DBMS’es want them really, really want thembad.
And… Ceph also does :) you should '''only''' buy SSDs with supercaps for Ceph clusters. Even if you consider NVMe — NVMe without capacitors is WORSE than SATA with them. Desktop NVMes do 150000+ write iops without syncs, but only 600-1000 iops with them.
Another option is Intel Optane. Intel Optane is also an SSD, but based on the different physics — Phase-Change Memory instead of Flash memory. Specs say these drives are capable of 550000 iops without the need to erase blocks and thus no need for write cache and supercaps. But even if Optane’s latency is 0.005ms (it is), Ceph’s latency is still 0.5ms, so it’s pointless to use them with Ceph — you get the same performance for a lot more money compared to usual server SSDs/NVMes.