Which drive should I use for SLOG?

[justjosh]

Hey guys,

I have a 6x14TB Z2 array that is painfully slow with sync=always.

I have a couple of surplus drives lying around that I feel could be put to better use. Which of these drives would be the best choice as a SLOG and why?

1. MZ1LV960HCJH-000MU Samsung PM953 960GB M.2 PCIe NVMe (TLC) 1.3DWPD, Unknown Endurance
2. HUSSL4040BSS600 HGST Hitachi 400GB SSD SAS 6Gbps (SLC) ~35PB Write Endurance
3. HUSMM1640ASS201 HGST Hitachi 400GB SSD SAS 12Gbps (MLC) ~7PB Write Endurance

I believe the Samsung has PLP capacitors while the HGSTs have "power loss data management algorithm".
Endurance wise I believe the HGSTs blow the Samsung out the window.
Latency wise the NVMe should be a clear winner over SAS.
Cost wise the HGSTs are slightly cheaper than the Samsung.

Thanks!

 

[kspare]

If you want it to last..use the 500gb slc drive.

 

[firesyde424]

What drive you use comes down to what your use case is and what your expectations are. If you plan on writing a ton of data or you expect that you will use this particular pool for more than 3-5 years, then you will want the drive with the higher write endurance. If you are looking for the best performance, the M.2 drive is your best option.

 

[justjosh]

What drive you use comes down to what your use case is and what your expectations are. If you plan on writing a ton of data or you expect that you will use this particular pool for more than 3-5 years, then you will want the drive with the higher write endurance. If you are looking for the best performance, the M.2 drive is your best option.

Will I be able to fully saturate the speed advantage of the NVMe?

 

[kspare]

I doubt it. thats why id opt for the drive that can handle the wear and tear.

 

[jgreco]

Will I be able to fully saturate the speed advantage of the NVMe?

No, of course not. You have six hard drives. On a good day, their velocity is nowhere near the speed of an NVMe drive, even if you threw the whole NAS out of an airplane to give it a boost.

 

[ChrisRJ]

"Back in the days", the recommendation was to go for SLC only.

 

[jgreco]

"Back in the days", the recommendation was to go for SLC only.

Sure, but the number of possible options has exploded since then, and SLC-only SSD's have become a rarity in the latter half of the 2010's. Now instead of meager high end offerings like the STEC ZeusRAM that still sit at the end of an SAS channel and can handle high-five-figure IOPS, you have choices such as Optane or the up-and-coming final ultimate winner, NVDIMM.