FS of choice for max random iops ( Maildir )

freebsd at top-consulting.net freebsd at top-consulting.net
Fri Sep 16 13:57:54 UTC 2011

Quoting Terje Elde <terje at elde.net>:

> On 16. sep. 2011, at 12:31, freebsd at top-consulting.net wrote:
>> Right now I defined an entire array of 8TB ( all 16 disks )  
>> separated in two pieces. 50 GB for FreeBSD to boot and the rest  
>> available to configure as storage.
> ZFS will want to write to it's ZIL (zfs intent log) before writing  
> to the final location of the data. Even if you're not waiting for  
> the ZIL-write to disk (because of the controller ram), those writes  
> will probably make it through to disk. That gives you twice as many  
> writes to disk, and a lot more seek.
> If you want to take zfs for a proper spin, I'd like to sugget adding  
> two small SSDs to the setup, mirrored by zfs. You can use those both  
> for the ZIL, and also as cache, for the array. That's a fairly small  
> investment these days, and I would be surprised if it didn't  
> significantly improve performance, both for your benchmark, and real  
> load.
> Note: you might be in trouble if you loose your ZIL, thus the  
> doubling up. I *think* you can SSD a cache without risking dataloss,  
> but don't take my word for it.
> Terje

I know it's usually a big no-no but since I have the battery backed-up  
write cache from the raid card, can't I just disable the ZIL entirely ?

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