Boot drive on pool

[Robti]

Hi is there any benefit of installing the os on a pair of 120Gb ssd drives rather on a single for a simple home media/ file backup setup ?
Thanks

 

[elvisimprsntr]

redundancy, if that is important to you

 

[Constantin]

… and potentially faster revival if one of the drives fails. However, depending on when and which boot drive fails, you may need to redo the boot settings in the motherboard BIOS. Unlike ZFS, the motherboard typically tracks the boot drive by hardware SATA slot / USB port, not UUID, serial number, or some other permanent attribute associated with the boot drive itself.

 

[joeschmuck]

Hi is there any benefit of installing the os on a pair of 120Gb ssd drives rather on a single for a simple home media/ file backup setup ?

In my opinion, only if you are a remote administrator and have remote BIOS access to reconfigure the boot drive if needed. Let me explain...

When your computer boots up it looks for a bootable drive, lets say drive 1 normally boots the system and drive 2 is the next in order. Well that sounds nice an all until drive 1 boots up halfway and crashes. Drive 2 won't do a thing and your system is not operational. If you have remote access to the BIOS then you can reconfigure to boot from Drive 2 and all will be good in the world until you can physically access the device to repair it. This is what @Constantin is saying above, I just gave you the example of a failure.

So let's say this is a home server and it crashes, well you can access the BIOS and change the boot priority to get your system operational. but is it worth the cost? Not in my book.

It takes very little time to reinstall the FreeNAS/TrueNAS application and then restore your configuration file, maybe 15 minutes if you are familiar with it all to have the system operational again.

My personal advice is to run a single SSD as a boot device and be happy that you have minimized your hardware configuration. Maintain a backup of your configuration anytime you make a change to your configuration. And to be honest, a home user is apt to make very little configuration changes once you have your system established.

And there are folks who will say that I'm incorrect, that adding a second SSD will save you a lot of pain but I just don't see the pain in the first place. Also, you could set up an emergency USB Flash Boot Drive if you desired and have it ready to go.

 

[Constantin]

Funny thing is, despite being a home user, despite having nearly 98% daily access to the server, I still prefer running a Z3 data pool and a mirrored boot pool.

While I agree that getting a new boot drive is not necessarily challenging and should be something we are all familiar with as part of a disaster recovery plan (y’all checked the expiration on your MRE’s, water containers, and flashlights monthly, too, ammirite?) I love knowing that, at worst, all I have to do is either reconfig the BIOS boot order or swap the extra SATADOM over one slot. Oh, and swap in cold spare I have here as well.

 

[Robti]

Thanks everyone after all the help I will be staying with a single as the spare is only 111Gb and the boot is 119 and I only asked while waiting for a couple of ironwolf drives to be delivered
Thanks

 

[Constantin]

Boot drives can be different sizes, though IIRC you have to start with the smaller one, add the bigger one, and then the boot pool capacity will reflect the capacity of the smaller drive. Adding a smaller drive to an existing boot pool with a higher capacity is likely not allowed. Both of my current SATADOMs were created/cloned by being added to a boot pool. The first one as a clone to the OEM 16GB SATADOM. Once the cloning was complete (I waited a week), the 16GB SATADOM was disconnected in the GUI, the next 64GB SATADOM was added, and I ended up with a 64GB mirrored pool (auto-expanded capacity, just like a ZFS data pool would).

I love how TrueNAS takes care of everything re: the boot pool in the background - formatting, cloning, and so on but I wish there was a dashboard, system alert or like indicator to show cloning progress / mirrored drive status. At the moment, boot pool is set and forget. Unless you get a system alert that one of the boot pool drives failed, it simply fades into the background. Yet for BIOS start-up disk setting purposes, you won't know when its safe to switch from one drive in the boot pool to the next via the GUI.

 

[NugentS]

@Constantin Have you noticed in the tech specs for the SataDoms that they specifically do not recommend use of RAID and even mention mirror specifically? https://www.supermicro.com/datasheet/datasheet_SuperDOM.pdf

Also, why the 64GB - better endurance?

 

[Constantin]

I believe you are misreading the tech spec.

The first thing SuperMicro says is that these SATADOMs are perfect for applications with many reads and relatively few writes, like boot OS disks. At a rated 1DWPD, I doubt my SATADOMs are even starting to get broken in.

The later section you reference has to do with SLOGs and other write-intensive applications that someone might be interested in since SATADOMs are small, may fit right onto the motherboard, and yet offer enough capacity to easily swallow a transaction group or two. In other words, someone might be tempted to set up a mirrored SLOG pool based on SATADOMs in the mistaken belief that these SATADOMs are suitable SLOG devices, experience a bad hair day, and then blame Supermicro. Hence also the multiple references to avoid using SATADOMs for other potentially write-heavy stuff, such as VMs.

Lastly, if there was no intent for mirrored boot disks to be SATADOMs, why would Supermicro put 2 SATADOM ports on my motherboard? Why the added expense if a simple SATA port would have been advised? SuperMicro takes incredible care designing their boards, these kinds of mistakes are not made. Too many of their boards feature multiple SATADOM ports for this to be a coincidence.

As for the 64GB limit, the cost delta was not great and I'm lazy enough where the 16GB OEM module had to remind me once or twice that it was 80% full and get off my lazy bum and free up some space. With 64GB modules, the capacity is so great that I can literally forget to poke around those settings for a year and still have oodles of space free before I nuke older FreeNAS/TrueNAS editions.

 

[NugentS]

I have to admit it didn't make a lot of sense to me and whilst not cheap, they are cheap enough that I don't care. I also use them as a boot mirror (although I use the 16GB ones). SLOG makes no sense at all, I never even considered them for that - no way are they quick enough at 75 or 180MB/s.

 

[Constantin]

It speaks to Supermicros cautious approach re technical specs that they highlight how not to use their equipment vs. the misleading specs that some other OEMs routinely release with their products suggesting amazing performance, usually under a very narrow set of conditions not found in real life.

for example, SSD manufacturers who marry a faster cache up front with slow flash in the back (not unlike SMR HDD drives). May work ok for a limited set of tests but falls flat under heavy use.

anyhow, I happily still use the original 16GB SATADOM that came with my ~2016 Mini XL (on it’s fifth motherboard by now). When used as intended, SATADOMs are likely as robust as the other SuperMicro gear.