Unraid with Optane cache drive

[StupidServerDude]

Does anyone have experience with using Intel Optane as a cache drive with Unraid?  I'm switching my home server over to Unraid next week since I'm tired of ZFS eating all of my RAM when I'm trying to run VMs and don't feel like setting everything up manually under Linux.

[NunoLava1998]

I don't know much about Optane, but I heard that ZFS is really good on drives like these:

https://www.amazon.com/Intel-Optane-800P-58GB-XPoint/dp/B078ZJSD6F

 

Optane 800P is slightly different than 900P:

• Smaller capacities (58GB/118GB rather than 280GB/480GB)
• PCIe x2 instead of PCIe x4 (this cuts the sequential speeds in half but 4K speeds are gucci)
• Uses M.2 instead of PCIe
• However, 4K speeds remain largely the same.
• Doesn't cost arm and leg

[porina]

No experience in that specific area, but Optane is essentially a fast SSD so should be fine.

[unijab]

If you set arc max to a limit that leaves enough for your VMs... You could keep using zfs

[StupidServerDude]

For anyone that finds this in the future, the Optane 900P 280GB PCIe one works great with dual Xeon E5-2670v2's.

[AMDKilla]

Optane's main purpose is to be used as a buffer when reading data off of spinning drives. It learns what data you use regularly and stores it on the Optane drive. It still increases write performance too, as it's faster, higher capacity and less volatile than your HDD's cache.

But UnRAID's only use for cache drives is for write performance. It uses it as a buffer for writes to the array only. So you won't see a read performance boost. You'll still see a write performance increase as long as Optane supports Linux, but you won't gain read performance (which is Optane's main perk).

[StupidServerDude]

On 12/31/2018 at 4:19 AM, AMDKilla said:

Optane's main purpose is to be used as a buffer when reading data off of spinning drives. It learns what data you use regularly and stores it on the Optane drive. It still increases write performance too, as it's faster, higher capacity and less volatile than your HDD's cache.

But UnRAID's only use for cache drives is for write performance. It uses it as a buffer for writes to the array only. So you won't see a read performance boost. You'll still see a write performance increase as long as Optane supports Linux, but you won't gain read performance (which is Optane's main perk).

Yeah I noticed that after I set it up... I ended up switching back to CentOS with ZFS (but now using the Optane drive as a cache) because of the generally awful performance.  The reading was fine I guess and the write performance after the cache was full was just unusable for me.  The web GUI was really nice so it was a shame.  Ironically I wish unraid supported some kind of software RAID or at least ZFS.

[StupidServerDude]

On 12/24/2018 at 10:22 PM, unijab said:

If you set arc max to a limit that leaves enough for your VMs... You could keep using zfs

I tried that in the past, but I actually noticed a significant performance decrease going from letting it use 100+GiB of RAM to 48GiB (I have 48TB of raw drives, I read that was the recommended minimum).

I ended up doing a hardware trade so I have 512GiB of RAM in my server so it shouldn't be a problem anymore.

[Electronics Wizardy]

On 12/24/2018 at 12:26 PM, StupidServerDude said:

Does anyone have experience with using Intel Optane as a cache drive with Unraid?  I'm switching my home server over to Unraid next week since I'm tired of ZFS eating all of my RAM when I'm trying to run VMs and don't feel like setting everything up manually under Linux.

ZFS doesn't use much ram, its using ram as a read cache. Everyfile system does this(including unraid) so unraid won't help you here.

 

Look at proxmox if you want better vm support. You can use btrfs, zfs and others to manage storage on it. Its also free.

 

There really won't be a benfit here, and optane is a waste here. 

 

The cache on unraid is for writes only, and optane isn't that fast for writes, normal nand drives are often faster, and you probabaly dont' need the endurance.