Controlling memory allocation - or is it wasted?

Controlling memory allocation - or is it wasted?

Postby nickandshuna » Wed Aug 03, 2011 4:35 am

So far I have seen memory increased in the Ready NAS Pro editions, the -100 series to 4096 after the video reservation was removed (which I have implemented) and now that I have recently purchased a -200 series (i.e. RNDP6000-200 o) I would like to know if you can utilise the additional memory specifically for disk cache.

Background: I use my NAS's purely for iSCSI for ESX4.1i using vSphere Enterprise Plus on a single Data Centre with two, 3 node clusters running HA and DRS. The NAS is only presenting iSCSI volumes nothing else (apart from the mandatory https for Front View). In the total, Cluster 1 runs 86546MB RAM and 60916MHz CPU and Cluster 2 about half that.

Environment: The RNDP600-100 series has 4096 with 6x2TB Caviar Blacks (4k version) - This obviously struggles during storage vMotion within it's self and when the guests are experiencing high I\O conditions, hence the purchase of a Second RNDP6000-200 populated with 6x Western Digital VelociRaptor WD3000HLFS 300GB @ 10K for performance (i.e. high I\O volumes and guests will reside). All ESX hosts (bar one) have dedicated Quad Port HBA's (bnx2i) initiating iSCSI at the BIOS for block level transport for iSCSI traffic on dedicated vlan's crossing 2 Dell Power Connect 6248 switches aggregated with 802.3ad trunks to the RNDP's, so the bottleneck is the storage.

Goal: The RNDP's have memory, lots, well my -100 series is maxed and 4GB is a decent amount of cache (if utilised), however I want to utilise this memory purely for Cache, ideally write (8GB would have a significant performance benefit here I would imagine), again for obvious reasons.

Predicament: If I were to upgrade the -200 series to 8GB, can this be utilised for disk write cache? or will it sit idle and not utilised at all? Is there a way within the NAS to reserve a percentage dedicated to write and read as do hardware RAID Controllers in servers and Service Processors in SANS?

Any help would be appreciated.

BTW - this type of feature would make the Business Editions of the ReadyNas appliances have a significant advantage both functionally and marketing wise (well as far a feature set to that of it's competitors in its class).

Regards,
Nick
nickandshuna
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