Wayne的雲端豆知識～

vSAN 6.5(含) 以前為255GB vSAN 6.6以後最小能夠再切分8等份(約32GB) vSAN 6.6 機制改良... Rebalancing protocol updated to accommodate various scenarios more effectively.  Previous limitations included inability to break large component (255GB) into smaller pieces. Rebalancing of large components sometimes lead to less than ideal placement decisions During reactive rebalancing, vSAN™ can now break large components into chunks If vSAN™ can find a new disk for the component without the need for breaking up into multiple components, it won’t break up. If vSAN™ can’t find a new disk without breaking, it will break into 2, and retry previous step. Will proceed with this logic of more splits up to 8 vSAN 6.5 機制如下...

How does write operation work Once a write is initiated by the application running inside of the Guest OS, the write is forked to both the write cache on the host which is the ‘owner’ of the storage object, and also to the write cache on the remote host or hosts which contain a replica. How does cache trigger write back At regular intervals, the SSD write buffer is de-staged to HDD. About Number of disk stripes per object The  Number of disk stripes per object  setting in the VM Storage Policy means stripe across “at least” this number of magnetic disks per mirror”. How to perform syncing under abnormal status components never move resync->if a server is down reblanace->if one HDD has over 80% utilisation rate, 20% of data will be moved absent (default 60mins) will trigger recovery/this is also the windows for offline mantainess How to test availability test FT by delete disk group is a correct way A 4GB VMDK with width set ...

vSAN Enterprise版本的vSAN Stretched Cluster功能，實際上就是在安裝過程中可以選擇建立Stretched Cluster的選項，選擇後可以看到(比起只建立fault domain)有多設定witness的步驟 事實上，Fault Domain與Stretched Cluster的不同，關鍵也在witness的設計 Stretched clusters essentially build on what fault domains did, and now provide what might be termed “data center awareness”. VMware vSAN Stretched Clusters can now provide availability for virtual machines even if a data center suffers a catastrophic outage. 更多訊息： https://storagehub.vmware.com/#!/vmware-vsan/vsan-stretched-cluster-2-node-guide/vsan-stretched-clusters-vs-fault-domains/1 http://vsanteam.info/vsan-stretched-clusters-click-click-done/

關係圖 http://gofile.me/6tQSF/2omq8AYOh Reservations > Distributed logical router > 僅顯示有Uplink的DLR Reservations > Distributed logical router > Network Profile 當Blueprint On-Demand Routed Network選擇這個Profile時連接到哪個DLR (目前測試一對多會輪替去接DLR) Blueprint > On-demand Routed Network > External network profile 定義此網路實際上會接到哪個DLR(由Reservations > Distributed logical router > Network Profile定義Mapping) Blueprint > On-demand Routed Network > Parent network profile 定義佈建出來的網路IP Range / Gateway  *使用On-Demand Router時External Network Profile看來只用來作Mapping不會實際用裡面的網路設

vSAN 是否支援 Air-gapped Switch 架構如下？如果發生以下情境，是否還能保持vSAN可用？  若是以上設定，只能在Switch失效時提供高可用性，若是單一Server線路或是網卡失效，此Server會被視為斷線 此外，根據下面官方說明 https://storagehub.vmware.com/#!/vmware-vsan/vmware-r-vsan-tm-network-design/advanced-nic-teaming/1 VMware’s is not recommending this topology. One of the main reasons for not recommending this network configuration is that failure of components, such as NICs on different hosts residing on the same networks, can lead to interruption of storage I/O. 如果真的需要Air-gapped Switch 架構，建議啟用LACP在不同的Switch以達到... 1.線路/網卡以LACP提供高可用性 2.Switch以兩台Switch提供高可用性