Best to boot from a ZFS pool or SATADOM

[alaint]

Hi,


My setup ..
- mb: Supermicro X8DTL-iF-O
- cpu: 2x E5620
- mem: 24Gig ecc
- 1x Intel X540-T1
- sata: 1x Supermicro SATA DOM 64Gig
- sata: 4x HGST 3T
- On average, my systems Uptime 400-500 days.


My intention ..
I want to stick to ZFS RAID10 for my VM/CT.
I recently discovered ZOL and got addicted.


My dilemma ..
Install my booting partition on the ZFS pool (rpool) and eventually use the DOM for cache.
or
Install Proxmox on the DOM and then create my ZFS pools.


The question ..
I always used a DOM for my OS (Proxmox) and then created my VM/CT/Storage area.
I recently started upgrading to Proxmox v.3.4 and discovered that the proxmox install iso can build a bootable RAIDz from the start.
This seem like the best of all worlds (for me) until I saw a post about a grub restriction with zfs, possibility of having a non bootable ZFS after losing a drive.


Replacing a bootable DOM by recovering from a working disk image is easy, but will bring the system down for the re-imaging time.
Replacing a drive on a zfs pool is easier and will not bring the system down. And I can take advantage of that DOM for cache, even if i do not know yet if this will make a big difference.
But, how much trouble can I get into at the next reboot, will my rpool still boot ?


What would be your expert recommendation, should I put the OS on DOM or the rpool ?
I'm having a very hard time to decide and at this point any input will be welcome.


thanks,
alain
ps- On another subject, I think you guys at proxmox are amazing, but to productive .. i find it impossible to follow your EOL :-(.

 

[wolfgang]

Hi,

I thing to use a SATADom with 64TBW as zfs cache is not a good idea.
I would buy a intel Pro 2500 120 GB as cache.
It cost about 100 Eu.

Then you have a super fast ZOL VM storage and a dedicated os drive.

 

[alaint]

Wolfgang, thank you

I was not aware that 64TBW (TeraBytes Written) would not be enough, for reliable long term caching.

I would love to put everything on a ZFS Root Pool, but I m afraid the booting process may get broken with a update (or after replacing a drive).
I guess, I will do what I always done and install the OS (Proxmox) on the DOM.
Then create my ZFS pool, without dedicated cache, hoping performance will be good enough ... there is no room for a extra drive.

 

[sigxcpu]

It is not about the size. Most likely a SATA DOM will be obliterated by the cache I/O.

What I did: I have a 32GB USB SSD (Transcend something). Installed Proxmox on it and created a big zpool out of the mechanical drives for VM/CT storage. If you really want L2ARC and/or slog, then you will need to buy a proper SSD, as suggested by wolfgang.

 

[mir]

If you really want L2ARC and/or slog, then you will need to buy a proper SSD, as suggested by wolfgang.

Intel DC S3510 comes cheap these days -> 80GB can be found to 100$ or 80€.