Use of SSD

[laurens]

Hi

I have a 40GB SSD and 4 WD disks of 4TB.
The 4 disks are in ZFS (2 by 2 mirrored and then striped). So I have about 8TB.
I have 32Gb RAM in it.
I only have NFS and AFS enabled, no SAMBA.
Loosing data when writting (RAM) is not important, it are always copies.
The installation was made on the SSD as "Embedded" OS + DATA (no swap partition)".
Can I use this unnesed part of the SSD to improve something of the ZFZ or is the only thing I can do mount it and make a new (not mirrored) share of it?
Would be nice if I could improve the speed of the file system returning all the files and folders, that's a bit slow somethimes.
I don't know if it's safe to reformat the partition from the GUI to something else without loosing the OS?

- From what I have read here, making it a cache has more negative then positive effects. I have 32GB ram and only sequential reads of large files. No random reads and almost dubble reads of the same file.
- Making it a ZFS log disk seems to be useless as I don't have (running) databases on the storage. So I guess ZFS Intent Log is disabled or small then.

[ChriZathens]

Did you use zfskerneltune?
If not then your system is not using your 32GB of RAM the best way. Install it and set it for 32GB.

If you want to use your ssd for cache you can use a usb to install embedded and use the ssd for anything else you like. The use of an ssd for the embedded is a waste , since it is not used- the OS is loaded to RAM on boot. The only advantage is faster boot than the usb stick.

[laurens]

Is that the "Enable tuning of some kernel variables" option under advanced? Or this old manual plugin? viewtopic.php?t=1278

[crowi]

Or this old manual plugin? viewtopic.php?t=1278

Yes, this one

[laurens]

Ok thanks for the tips!
The reason I took an SSD instead of an USB disk is to keep it all inside the box. Thought I could use an internal USB device.
It should become solar powered on batteries (off grid) so a fast startup is always handy because I will power it off when their is no access to it and at night.
On the topic I have found out these variables:

Code: Select all

# ZFS v28 kernel tune
vfs.zfs.prefetch_disable="1"
vfs.zfs.txg.timeout="5"
vfs.zfs.vdev.max_pending="10"
vfs.zfs.vdev.min_pending="4"
vfs.zfs.write_limit_override="0"
vfs.zfs.no_write_throttle="0"

# X64_32GB
vm.kmem_size="30720M"
vfs.zfs.arc_min="28672M"
vfs.zfs.arc_max="28672M"

But I now just enabled those:

1.jpg

Because:
- I have seen my RAM go to over 40% before any tuning
- On https://wiki.freebsd.org/ZFSTuningGuide I read this: "FreeBSD 7.2+ has improved kernel memory allocation strategy and no tuning may be necessary on systems with more than 2 GB of RAM."
- I see for example "vfs.zfs.prefetch_disable="1"" is mainly for a lot of random reads, which I don't have.

[b0ssman]

set vfs.zfs.prefetch_disable to "0"

you want prefetch to be enabled