ZFS: ZIL device export/import

[Ronald Klop]

On Sat, 13 Apr 2013 20:25:40 +0200, mxb <mxb at alumni.chalmers.se> wrote:

>
> On 13 apr 2013, at 20:10, "Ronald Klop" <ronald-freebsd8 at klop.yi.org>  
> wrote:
>
>> The L2ARC is considered empty on startup/import. The ZIL might contain  
>> valuable data after a crash. So your setup is wrong. The ZIL is  
>> supposed to be one-on-one with the pool. You should move the ZILs to  
>> the JBOD. You can make a mirror of the ZIL devices to improve failsafe  
>> operation by redundancy.
>
>
> I figured that out with mirror, thus my tests with slices - one slice on  
> local SSD (per HU) the second half of the mirror on JBOD-slice  
> (dedicated SSD there too). But this requires extra 'zpool online' and  
> 'zpool replace'.
>
> As I understand there is no other way??
> I'm forced to do those steps?
>
> ZIL dev. on JBOD is a bit odd - the idea with local (per HU) ZIL is to  
> postpone transfer of the data over SAS Expander.
> Or at least buffer and then move over SAS Exp. .
>
> //mxb

I thought the idea of ZIL is a fast buffer before the write to slow disk.  
Are you really sure the SAS expander is the bottleneck in the system  
instead of the disks?

Ronald.