Dell PowerEdge R720 with H310 Setup

[IronSheepdog]

I will be receiving my Dell Poweredge R720 tomorrow. I made sure to get the H310 controller. I'm needing some information from anyone who may know this. What I want to do is configure two disks in a hardware RAID 1 for the Boot/OS drive. However, I want the other 6 disks to be controlled by TrueNAS in a RAID Z2 configuration. Is this even possible with a H310 in IT mode? Or does IT mode pretty much ruin all change of hardware RAID?

If this is not possible, what is everyone doing for their boot/OS drive? I hate to have it on one disk with no redundancy. Or is everything just making sure they have a backup somewhere else?

 

[jgreco]

Highly Available Boot Pool Strategy

I've pounded a few versions of this out over the years, but I hate explaining over and over. TrueNAS allows a ZFS boot mirror pool to be created to increase the reliability of the NAS. This sounds great in theory, but there's a flaw. Due to...

www.truenas.com

 

[HoneyBadger]

There's minimal configuration stored on the boot device, and unless you're planning to measure your uptime in "nines" it's not worth it for most home users to do redundant boot. Get a USB-to-SATA converter, attach it to a small inexpensive SSD, and boot from that. It's generally not worth sacrificing two drive bays for it.

Now if this is for a business, where downtime loses dollars, or you just want to answer the question of "why?" with "why not?" then @jgreco has it covered quite nicely in his resource guide.

 

[artlessknave]

hardware RAID 1 for the Boot/OS drive

do not do this. truenas boot drive runs zfs. just make a mirror with any HBA, (or USB's if you are really short on HDD bays), and make your pool on the same HBA. this is the recomended config for a reason.
not only is there no reason TO do this, there ARE reasons NOT to do this.
Jgreco and many others have written why.

 

[IronSheepdog]

Highly Available Boot Pool Strategy

I've pounded a few versions of this out over the years, but I hate explaining over and over. TrueNAS allows a ZFS boot mirror pool to be created to increase the reliability of the NAS. This sounds great in theory, but there's a flaw. Due to...

www.truenas.com

A lot of that is Greek to me. I'm not as understanding on that topic yet. To be honest, I can't even tell if that answered my questions or not.
EDIT: So basically don't do a redundant boot is what I'm guessing; at least not in a RAID.

There's minimal configuration stored on the boot device, and unless you're planning to measure your uptime in "nines" it's not worth it for most home users to do redundant boot. Get a USB-to-SATA converter, attach it to a small inexpensive SSD, and boot from that. It's generally not worth sacrificing two drive bays for it.

Now if this is for a business, where downtime loses dollars, or you just want to answer the question of "why?" with "why not?" then @jgreco has it covered quite nicely in his resource guide.

Well, yes this is for home use. However, I do a lot of video editing. I can't afford to have the server go down for an extended period of time and have to reinstall everything. When you say a USB to SATA controller, you mean mounting a SSD on the outside of the case?

 

[artlessknave]

So basically don't do a redundant boot is what I'm guessing.

no, redundant boot is fine, just usually not zfs on top of RAID. TrueNAS already provides excellent redundant boot. built in.

I'm fairly advanced with TrueNAS, and I read the "high availability boot pool" thing, and don't really understand the point. 2 SSD's are pretty damn reliable already, and while for reasons unkown to me IX decided to make it impossible to 3-way mirror the boot pool in the webUI, it is possible to get around that, such as by installing to 3 drives.

running on top of RAID when pretty much everywhere ZFS specifically recommends NOT running on top of RAID doesn't make any sense to me, especially when recomeding setups for new users, for whom making catastrophic mistakes with ZFS is really easy.

if you are an advanced TrueNASer, and you have your backups and understand the risks, sure, put the whole pool on RAID, but for a new user?

 

[jgreco]

I read the "high availability boot pool" thing, and don't really understand the point.

The point is that your PC BIOS will not boot from the secondary device in a ZFS setup if the primary device is only partially failed. For example, if you have two El Cheapo 60GB SSD's and the one on SATA 0 develops an inability to read the boot LBA's, your BIOS will nevertheless see that SATA 0 is present and try to boot from it, fail, and hang with the dreaded "Disk Read Error" message or whatever your particular BIOS does.

A HBA in IR mode allows the HBA to notice that it is getting a read error on SATA 0 LBA 0, and will fail over to SATA 1 LBA 0, and present that data to the host, thereby allowing bootup.

This does not completely eliminate every possible impediment to booting, but it does get rid of a major one.

running on top of RAID when pretty much everywhere ZFS specifically recommends NOT running on top of RAID doesn't make any sense to me,

The reasons not to run on RAID are explained in my article

What's all the noise about HBAs, and why can't I use a RAID controller?

1) An HBA is a Host Bus Adapter. This is a controller that allows SAS and SATA devices to be attached to, and communicate directly with, a server. RAID controllers typically aggregate several disks into a Virtual Disk abstraction of some sort...

www.truenas.com

and as it turns out, the most devastating reasons not to use a RAID controller do not apply to an HBA in IR mode. There's no cache, there's no battery, there IS a highly ZFS-compatible driver, etc. The IR mode does hide the state of the component disks from ZFS, and also hides the redundancy, which is why you might do some sas2ircu scripting to check the state of the boot device, and also why you pair it with a third SSD to provide the ZFS-level redundancy.

if you are an advanced TrueNASer, and you have your backups and understand the risks, sure, put the whole pool on RAID,

Nobody's advocating such an idiotic thing as running your data pools from RAID. The highly available boot pool thing is a very special case that is only intended to handle the bootstrap from BIOS issue.

 

[artlessknave]

The point is that your PC BIOS will not boot from the secondary device in a ZFS setup if the primary device is only partially failed.

ahhhh. it all makes sense now. I did not get that from that article.

 

[jgreco]

ahhhh. it all makes sense now. I did not get that from that article.

Well the second sentence does say

Due to the design of the average PC BIOS, a boot device that has become corrupted but not failed entirely may prevent booting.

but I suppose that could be taken several different ways. Mmm.

 

[jgreco]

ahhhh. it all makes sense now. I did not get that from that article.

Interestingly enough the very next thing in the moderator approval queue is potentially an example of this:

TrueNAS 12.0-U7 gptzfsboot : error 128 lba XXXXXXXX

Overnight, my NAS (crashed? then rebooted) then when I came in this morning, my TRUENAS 12.0-U7 is down. I checked the hardware (all=ok), I rebooted a couple of time but the errors messages are steady: While truenas boot is in progress, I have : gptzfsboot : error 128 lba xxxxxxxx ( repeated 8...

www.truenas.com

If you look at the attachments, the boot device has suffered some sort of issue.

 

[jgreco]

ahhhh. it all makes sense now. I did not get that from that article.

If you have a moment, can you eyeball the resource again and see if I've made it clearer? Thanks.

 

[artlessknave]

If you have a moment, can you eyeball the resource again and see if I've made it clearer? Thanks

it is much clearer. I can now see the point!

 

[jgreco]

I appreciate the feedback. I write this stuff for you folks, but it is hard to see all the ways in which my preconceived notions of the world may seep into my posts. I strive to make it clear and appreciate any help in doing so!

 

[artlessknave]

I know what it's like. I'm trying to do documentation at my job as well, and nobody likes to tell me it doesn't makes sense so i can fix it :/