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@xxxxxxxxxxxxx> 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 > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
