Re: CentOS MD RAID 1 on Openfiler iSCSI

[John R Pierce <pierce@xxxxxxxxxxxx>]

On 06/28/10 7:53 PM, Emmanuel Noobadmin wrote:
> The only problem is their HA is commercial only and costs more than
> the entire hardware budget I've got for this. Crucially, it relies on
> a failover/heartbeat kind of arrangement. According to some sources,
> the failover delay of a few seconds will cause certain services/apps
> to fail/lock up. Not an issue for the immediate need but will be a
> major no no for the other project I have in the pipeline.
>
> Which was why I was thinking of MD raid 1 on the application server
> site: no failover delay if one of the data server fails to respond to
> respond in time.
>    

ISCSI gets REAL sketchy on network failures.  it takes at least several 
TCP timeouts before it gives up and returns an error.  I do hope both 
storage servers have ECC so you're not mirroring a soft bit error at an 
inopportune time (Solaris ZFS would cope gracefully with this, but likes 
iscsi timeouts even less than dmraid)


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