Re: New server: SSD/RAID recommendations?

> Why would you think that you don't need RAID for ZFS?
>
> Reason I'm asking if because we are moving to ZFS on FreeBSD for our future projects.

Because you have zraid. :-)

https://blogs.oracle.com/bonwick/entry/raid_z

General points:

1. It's my understanding that ZFS is designed to talk to the hardware directly, and so it would be bad to hide the physical layer from ZFS unless you had to.
After all, I don't think they implemented a raid-like system inside ZFS just for the fun of it.

2. You have zraid built in and easy to manage within ZFS - and well tested compared to NewRaidController (TM) - why add another layer of management to your disk storage?

3. You reintroduce the raid write hole.

4. There might be some argument for hardware raid (existing system) but with software raid (the point I was addressing) it makes little sense at all.

5. If you're on hardware raid and your controller dies, you're screwed in several ways. It's harder to get a new raid controller than a new pc. Your chances of recovery are lower than zfs. IMHO more scary to recover from a failed raid controller, too.

6. Recovery is faster if the disks aren't full. e.g. ZFS recovers what it is there. This might not seem a big deal but chances are it would save you 50% of your downtime in a crisis.

However, I think with Linux you might want to use RAID for the boot disk. I don't know if linux can boot from ZFS yet. I would (and am) using Freebsd with zfs.

Graeme.

On 07 Jul 2015, at 18:56, Wei Shan <weishan(dot)ang(at)gmail(dot)com> wrote:

> Hi Graeme,
>
> Why would you think that you don't need RAID for ZFS?
>
> Reason I'm asking if because we are moving to ZFS on FreeBSD for our future projects.
>
> Regards,
> Wei Shan
>
> On 8 July 2015 at 00:46, Graeme B. Bell <graeme(dot)bell(at)nibio(dot)no> wrote:
> >
> > RAID controllers are completely unnecessary for SSD as they currently
> > exist.
>
> Agreed. The best solution is not to buy cheap disks and not to buy RAID controllers now, imho.
>
> In my own situation, I had a tight budget, high performance demand and a newish machine with RAID controller and HDDs in it as a starting point.
> So it was more a question of 'what can you do with a free raid controller and not much money' back in 2013. And it has worked very well.
> Still, I had hoped for a bit more from the cheaper SSDs though, I'd hoped to use fastpath on the controller and bypass the cache.
>
> The way NVMe prices are going though, I wouldn't do it again if I was doing it this year. I'd just go direct to nvme and trash the raid controller. These sammy and intel nvmes are basically enterprise hardware at consumer prices. Heck, I'll probably put one in my next gaming PC.
>
> Re: software raid.
>
> I agree, but once you accept that software raid is now pretty much superior to hardware raid, you start looking at ZFS and thinking 'why the heck am I even using software raid?'
>
> G
>
>
>
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> Ang Wei Shan