NFS NAS with SSD cache in front of RAID5 x 4 notebook drives (rust).
... a work in progress.
- It works.
- Very fast
- Cache is using Write Behind policy (how much trouble am I in?). OK, some testing shows that cache software checks that the SSD cache and the spinning rust are in sync at startup. If they are not (and I have no idea how it knows something happened) it sets about flushing the entire cache to the disks (presumably because it cannot tell which bits are out of sync). This flushing took a long long time, nevertheless everything was available and seemed quick enough during the process.
As pointed out by a good friend, the cache must be persistent for this to work (and SSD is, so all is good, nevertheless my fingers are crossed). - NFS Ganesha docker container (userland NFS server - replaces Samba)
- Raspberry Pi 4 x 4GB
- Sabrent USB 3 x 4 HDD 2.5 inch
ordered via AmazonAU from USA. Couldn't find this in AU.
Unit has, what seems, a massively oversize 12v 4A psu. It has a configurable power connector, but only came with US plug (more adaptors).
Possibly the most attractive piece of plastic for 2019. Brilliant plastic design. - Toshiba sub-credit card SSD
- References
Redhat Creating LVM Cache Logical Volumes
Kernel Device Mapper Cache
- ext4 fs read this: Forcing ext4lazyinit to finish its thing
Essentially ext4lazyinit runs in the backgraound chirping the RAID every few seconds. This causes the RAID drives to annoyingly stay awake forever, defeating the purpose of 2.5 inch drives which spin up really quickly (compared to the slow spin up of the old 3.5 iron which drives me crazy), not to mention wasting power.
https://superuser.com/questions/784606/forcing-ext4lazyinit-to-finish-its-thing - Fix fan noise: Added sophistocated fan controller (100 ohm resistor). Perfect. *essential*. Fan will probably last 10 times longer too.
Fix fan noise hack (note to self - add heatshrink over resistor ends)
LOL - Note sticker... +RED -BLACK (note to Chinese manufacturer +WHITE -BLACK (maybe)):
