Re: 10GbE / iSCSI storage for postgresql.

Dear Craig ,

The other end of the iSCSI shall have all the goodies like the raid controller
with a WBC with BBU. There can even be multiple raid cards for multiple
servers and disksets. I am even planning for NICs having TOE features .

The doubt is will it work withing a acceptable performance range as
compared to the situation
of DAS (Direct Attached Storage). Has anyone tried like this before ?

regds
mallah.

On Thu, Sep 22, 2011 at 9:44 AM, Craig Ringer <ringerc(at)ringerc(dot)id(dot)au> wrote:
> On 09/22/2011 03:49 AM, Rajesh Kumar Mallah wrote:
>>
>> Hi ,
>>
>> Can PostgreSQL run fast ( within 80% of DAS) with iSCSI sotrage
>> connected via 10GbE ?
>
> "Maybe".
>
> What's that 80% of? Sequential read throughput? Random IOPS? Individual read
> latency?
>
> What's the expected workload? Read-heavy, write-heavy, or middle-ground?
> Data warehouse/OLAP or OLTP? Lots of small simple transactions, or fewer big
> complex transactions?
>
> Does the system on the other end of the iSCSI link have battery-backed write
> caching, flash-logged write cache, or some other way to guarantee writes are
> persistent without having to wait for data to flush out to spinning disks?
>  You'll need something like this for decent write performance especially if
> you're doing lots of small transactions. If the SAN doesn't have a safe way
> to cache writes you can partly work around the issue by doing fewer bigger
> transactions and/or by using a commit_delay.
>
> What kind of read cache does the SAN have? How much contention with other
> users will there be? How big is its write-back cache (if it has one)? Does
> it have any kind of QoS to prevent something like someone disk-imaging a
> server from starving your Pg instance of read bandwidth?
>
> --
> Craig Ringer
>