Short-Take: iSCSI+Nexenta, Performance Notes

Here are a few performance tips for running iSCSI with NexentaStor in a Windows environment:

1. When using the Windows iSCSI Software Initiator with some workloads, disabling the Nagle Algorithm on the Windows Server is sometimes recommended;


2. Tuning TCP window and iSCSI parameters on each side of the connection can deliver better performance;


3. VMware part of the equation? Adjusting the way VMware handles congestion events could be useful;


4. On NexentaStor, disable the Nagle Algorithm with a value of "1" (default, 4095, enabled)

For storage applications where latency is a paramount issue, these hints just might help...

Update: FreeNAS and ESX 3i

NOTE: There seems to be a known problem with local pass-through RDM and LSI Logic SCSI controllers related to this post. FreeNAS running on ESX Server 3i using virtual disks from VMFS storage does not exhibit a failure problem, although the logging issue remains.

FreeNAS (0.69) and VMware ESX Server 3i (ESXi) would seem like a good "free as in speech" pairing for low-end virtualization. Unfortunately, the reality is not a good one. Mine's not the first problem with FreeNAS and VMware.

FreeNAS's iSCSI target and VMware ESX Server 3i (update 3) get along fine until you push the connection between them. Initially, ESXi finds the target, formats it and appears to be working fine: you can even create some light-weight VM's on the allocated storage. However, it's when copying VM's from one storage array to another where things go wrong.

SME Stack V0.1, Part 3 - Storage Solutions

If storage is the key, shared storage the key that opens all locks. In the early days of file servers, shared storage meant a common file store presented to users over the network infrastructure. This storage was commonly found in a DAS array - usually RAID1 or RAID5 - and managed by a general purpose server operating system (like Windows or Netware). Eventually, such storage paradigms adopted clustering technologies for high-availability, but the underlying principles remained much the same: an extrapolation of a general purpose implementation.

Today, shared storage means something completely different. In fact, the need for "file servers" of old has not disappeared but the dependency on DAS for the place where stored data is ultimately placed has moved to the network. Network attached storage - in the form of filers and network block devices - are replacing DAS as companies retire legacy systems and expand their data storage and business continuity horizons. Today, commercial and open source software options abound that provide stability, performance, scalability, redundancy and feature sets that can provide increased functionality and accelerated ROI to their adopters.