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伴隨著vSphere 6.7的發布，vSAN也一同更新。看似只是小版本號多了0.1，但新功能上的變化可是真不少。
下面我會貼出一篇國外網站（https://www.vladan.fr/vmware-vsan-6-7-announced）上的原文，同時加入了自己的一些理解。我不算這方面專家，如有寫錯之處望大家多指正：）
Adaptive Resync（自適應重同步） – dynamic management of resynchronization and VM traffic. While the previous release of VMware vSAN allowed putting a manual threshold on the resync operations and also to split large components during redistribution, the vSAN 6.7 goes much further and allows adaptive resync.
Adaptive resync will ensure that a fair allocation of resync resources are available for VM IO (IOPS consumed by VMs) and resync IO (IOPS consumed by the backend storage tasks). It all will happens during dynamic changes and load on the system. The adaptive resync will guarantee the level of bandwidth to ensure that specific traffic type will not starve from resources.
根據我的理解，Resync一般發生在數據重構（Rebuild）或者增/刪節點時的數據重平衡（Rebalance），Adaptive resync能夠保證同步I/O獲得至少20%的帶寬，而在沒有resync流量時則VM I/O可以使用全部100%的帶寬。
Faster Destaging（更快的數據下沉） – VMware has improved the in-memory handling of I/O during destaging. In fact, during the destage process from the write buffer to the capacity tier. So the buffer is available for new IOs much quicker.
This optimization provides better performance not only for VM I/O but also for the resynchronization I/O.
vSAN Replica Consolidation（副本合并） – It consolidates replicas which are stored across multiple fault domains (hosts) while maintaining FTT compliance. Before you shut down, you need to put host to a maintenance mode. You also need to select an evacuation method (Ensure data accessibility from other hosts, Evacuate All data to other hosts, or No data evacuation)…
The new improvement:
Opens up fault domain as a target for other objects during decommissioning.
It also looks for the smallest component to move.
As a result, there is fewer data rebuilt and less temporary space usage.
上面的動畫有助于理解這部分改進。我們知道在將vSAN集群中的節點撤出之前，需要先進入維護模式，此后面臨數據在節點間的移動以保證FTT規則（副本數量不變）。新功能所做的就是減少數據重構量和臨時空間占用。
Space efficiency improved via New Object Provisioning（通過新的對象分配改進空間效率） – It brings new behaviors with swap file objects for space efficiency. The new swap objects are thin provisioned（精簡配置）.
VM swap now Thin provisioned (previously an advanced parameter had to be set on a per-host basis).
A policy will be inherited from VM instead of the Default vSAN storage policy
FTT on swap object consistent with applied object policy
如果我沒記錯的話，vSAN之前已經允許將swap內存交換磁盤文件設置為thin，在Horizon VDI這樣的虛擬機密集型應用中，可以節約不少存儲空間。以前打開這個高級選項還比較麻煩，如今應該成為默認設置了。
Fast Failovers when using Redundant vSAN networks（當使用冗余vSAN網絡時快速恢復） – An Improved resilience of redundant vSAN networks.
New logic has been introduced.
Each vmknic is on a different subnet
no connectivity between switches
There is an immediate failover to other fabric when there is a failure of vmknic in one fabric
Optimized Witness Traffic separation for stretched clusters（針對延伸集群優化的見證節點流量隔離） – if you’re running an architecture with a stretched cluster environment, you’ll have a possibility now to benefit from the improved separation of witness traffic from vSAN data traffic. The new improvements will prevent data traffic from being routed via vmknic for witness host traffic when there is a link failure.
It’s configured by specifying an alternate vmknic (by ESXCLI command only in this release). This was previously supported already for 2-Node configurations.
Failure handling improved in case of stretched cluster architecture（延伸集群架構實例中的故障處理改進） – you’re in a situation of a site isolation. The inter site link is down (ISL) but also the link to the third site where the witness is located, is down as well.
In order to track the component health properly, in a situation when the connectivity to the Witness site is back again, vSAN will track the fitness of each site after full partition event of the Preferred site. The secondary site is maintained as an Active site until ISL connectivity is restored.
It prevents false positives when the ISL is not “up”.
Host Affinity for Next-Gen Applications（針對下一代應用的主機親和） – you can now “pin” a VM to a certain node.
The system makes sure that data stays on the same host that VM runs.
針對Hadoop這類有本地I/O優化的應用，vSAN現在允許限制虛擬機數據存放在本地物理服務器上，并且以單副本運行（HDFS等自身有多副本保護機制）。
Stretched Cluster Efficient Resync with Proxy Owner（通過代理節點的延伸集群高效重同步） – this feature’s goal is to reduce inter-site traffic. It minimizes the data which travels across WAN link.
It designs a proxy owner on the target site (Site B in our example) which takes advantage of local resync.
The partial resync will sync active replica across ISL.
It will establish proxy owner to manage local resync.
Resync of the replica on site B will occur from a local copy.
在跨站點（雙活）vSAN部署中，每個站點內部有副本保護，跨站點也是副本保護。在最初的延伸集群中，vSAN似乎對這些副本是“同等對待”的，也就是在恢復B站點的數據時，A站點的2個副本需要分別從Site A復制到Site B完成Resync，這樣對數據中心間鏈路的占用較大。
而在vSAN 6.7版本中，副本數據可以由Site A的代理Onwer節點跨站點只復制一次，在Site B的代理Onwer節點再將其本地Resync復制出多份。這樣就節省了WAN鏈路的數據流量。
Support for Windows Server Failover Clusters (WSFC，故障恢復集群支持) – now it supports the legacy storage architectures. iSCSI service which can be activated on the VMware vSAN cluster can present shared storage to those WSFC servers and the solution is fully supported. It supports either:
Physical – Using guest iSCSI initiator
Virtual – Using guest iSCSI initiator
vSAN Support Insight 智能支持 – when enabled, the data are anonymized and then uploaded to VMware. And it is VMware which is able to help when you’re experiencing problem or performance struggle. The pieces of information (such as names of hosts, or VMs) are changed before that information is uploaded to VMare.
Health Checks Additions and Improvements（健康檢查增加和改進） – there are some improvements on the health checks for vSAN 6.7 as well. Those health checks are very useful to troubleshoot or avoid problems.
New host maintenance mode verification ensures proper decommission state
New host consistency settings verification for advanced settings
Improved vSAN and vMotion Network connectivity checks
Improved vSAN health Service Installation check
Improved physical disk health check combines multiple checks (software, physical, metadata) into one check
Improved HCL check; firmware check now independent from driver check
Enhanced Diagnostic Partition (coredump) Support（增強診斷分區支持） – for diagnosing issues properly, there is a coredump partition. It is a special partition for diagnostic purposes. VMware vSAN 6.7 is automatically extending this partition when needed, depending on the host requirements. vSAN 6.7 needs larger coredump partition so it is able to automatically resize the coredump partition（能夠自動調整coredump分區）.
Support for 4Kn Disks – those are a large disk which has a better price per GB than 512e and 512n disks (supported already by the previous version of VMware vSAN). New 4kn disks are supported and the vSAN data plane I/O is optimized for 4Kn.
There is a software emulation for 4Kn.
vSAN 6.5已經支持512e扇區格式的HDD機械硬盤，但由于ESXi kernel的原因直到6.7版本才支持原生4kn磁盤。我們知道512e在未對齊寫入時性能會有影響，4Kn則好多了，除非是傳統應用發出小于4K的I/O，這種情況下才可能出現“寫放大”。
vSAN的數據路徑已經為4Kn優化，這個變化主要影響HDD而與SSD無關。
Improved Security with vSphere FIPS 140-2 validation（數據加密改進安全性） – VMware VMkernel cryptographic module v1.0 has achieved FIPS 140-2 so vSAN 6.7 takes benefit of this. It uses this FIPS 140-2 validate d cryptographic module implemented already in vSphere.
綜上所述，vSAN 6.7在之前版本基礎上帶來了一些重要的改進，可見軟件定義存儲（SDS）的腳步還會越走越遠。
翱翔云作為vSAN的企業級核心合作伙伴，旨在為客戶提供最先進的商業產品和解決方案，歡迎來電咨詢： 010-51669920-8881
2018-05-22
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