Slow mirrored tiered storage spaces

[kathampy]

In storage spaces tiering means moving hot data manually or automatically to the faster tier. It's not happening in real time. ( If I remeber correctly this process is started with the default settings at midnight or so ._.)

The WBC is also stored on the SSD tier, which is realtime caching. It's being bypassed in benchmarks.

I believe the SSD tier WBC is used in place of the OS's RAM based WBC, hence write-through mode bypasses it as well.

 

[i386]

Storage space (unlike zfs) doesn't use os ram for caching writes

All writes go the permanent storage (first wbc and from there to the hdds) and then are acknowledged to the applications.

 

[kathampy]

Storage space (unlike zfs) doesn't use os ram for caching writes

All writes go the permanent storage (first wbc and from there to the hdds) and then are acknowledged to the applications.

RAM cache is allowed (without SSD WBC) if you tell it you have a UPS.

 

[i386]

You can enable RAM WBC from PowerShell.

That's new to me...
I know that there is the powershell command with "IsPowerProtected" but it only enables the cache on hdds/ssd and not ram. Can you post the command which can be used to enable ram wbc?

 

[kathampy]

That's new to me...
I know that there is the powershell command with "IsPowerProtected" but it only enables the cache on hdds/ssd and not ram. Can you post the command which can be used to enable ram wbc?

IIRC this also enables a fixed 1GB WBC, or maybe the OS write cache. And this does fake the speed in CrystalDiskMark even though it uses write-through.