Creating Image file device in StarWind VSAN has some options that we'll discuss today. In this post, you'll learn How To Create a Stand-Alone Image File device in StarWind VSAN.
Image device can be configured with or without cache. The cache is used to speed up the processing of disk requests using a faster intermediate storage memory, which holds frequently used data.
What StarWind does, is that it creates a fully fault-tolerant and high-performing storage pool built specifically for the virtualization workloads. It basically mirrors the existing server’s storage and RAM between the participating cluster nodes. And creates shared storage via iSCSI export.
There are two cache policies you can choose from (Write-Back and Write-Through). The third option is No caching. Also, there is a First level cache (L1) and second level cache (L2). The L1 is RAM, so StarWind uses that fastest medium to accelerate and absorb writes. L2 cache uses Flash devices.
The cache configuration and Image file device creation are done through StarWind management console.
What's happening inside the cache is interesting too. There are data which are written into a cache, but when the cache is full, an algorithm chooses which items are obsolete and needs to be refreshed by new ones. StarWind uses Least Recently Used (LRU) algorithm for that.
Cache states are “Empty“, “Dirty” and “Clean“. Let' quote a few sentences about that:
In general, three cache states can be singled out depending on the level of the cache exhaustion: dirty, clean, and empty. At the beginning, all cache blocks are “empty” – the allocated memory holds no data, and cache blocks are not associated with disk blocks. They start being loaded with data during the working process. The cache block is considered “dirty” if user data was written to it, but has not been flushed to disk yet. In this case, the cache memory contains actual data while the disk stores irrelevant and older version of the data. The cache block is considered “clean” if the data it holds was also flushed to the disk (or the cache block was filled up as a result of disk read operations). In this case, the cache block and the corresponding disk store the same data.
It means that the cache is constantly updated with new data where old data are discarded.
StarWind Management Console
For all flash scenarios, you don't need to assign any L1 cache.
If you're using write-back with L1, you should have a UPS in order to configure a proper shutdown your StarWind nodes.
StarWind recommends using L1 cache in writeback mode and L2 in the write-through mode respectively in order to achieve high performance and additional protection.
The Image Device File creation Wizard
Basically, you must use the Add Device (Advanced) in order to create this file. From the StarWind console, chose Add Device (Advanced) and then follow the wizard which will guide you through the whole process.
You'll be creating a new Hard Disk Drive > Virtual Disk > Chose storage > Virtual Disk Options (Thick/Thin etc) > Policy choice. (see image below).
When adding the new image file (advanced), you have a possibility to define flash cache policy and size if necessary.
Specify Cache Parameters
Note: we won't go through the full config, as it's been detailed step-by-step at StarWind blog article. You can also download a PDF document from the same page there. Here are the sources.
Source: You can follow the full guidance on creating Stand-Alone image file device and the relation with L1 and L2 caches, in this post here.
Also worth to read: StarWind Virtual SAN L1 and L2 Caches
StarWind stand-alone image file device can be converted to Highly Available (HA) device. The guide on how to create HA device via StarWind VSAN can be found by following this link.
StarWind has also a Free version which can be used in production environments, did you know?
StarWind VSAN free version. Check below.
StarWind Virtual SAN FREE Version Features:
StarWind Virtual SAN Free is completely unrestricted: it is allowed for production use, supports all usage scenarios of the commercial version, has a perpetual license, and is not feature- or functionality-limited version of StarWind VSAN.
- No Capacity Restrictions – you can use as many capacities for your mirrors, as you like (previously restricted)
- No Scalability Restrictions – as many nodes as you like. (previously limited to 2-nodes only)
- No Time Limit on License – The Free license if for life. After 30 days, the only management option you’ll have is PowerShell or CLI.
- Production use – can be used in production, but if anything goes wrong, you will only find support through community forums.
- PowerShell Scripts – StarWind Virtual SAN Free is shipped with a set of ready to use PowerShell scripts allowing users to quickly deploy the Virtual SAN infrastructure.
- No StarWind Support – only community-based support.
- StarWind HA – The shared Logical Unit is basically “mirrored” between the hosts, maintaining data integrity and continuous operation even if one or more nodes fail. Every active host acts as a storage controller and every Logical Unit has duplicated or triplicated data back-end.
- No virtual tape library VTL as on the paid version.
StarWind allows creating tailored solution adapted on different hardware and architecture. It is a really flexible solution. However, there is a lot to know in order to follow best practices for different scenarios. I'd recommend getting in touch with StarWind folks through their forums in order to get help, or buy support when you're trying to implement your own solution.
More posts about StarWind on ESX Virtualization:
- Hybrid IT With Active-Active Cloud Storage – StarWind Solution
- StarWind Supports SMB3 – Did you Know?
- Veeam 3-2-1 Backup Rule Now With Starwind VTL
- StarWind and Highly Available NFS
- StarWind Storage Appliance Protects up to 4 disk failures
- How-To Install Hyper-V Cluster 2-Node Windows Server 2016 With StarWind Virtual SAN
- VMware VSAN Ready Nodes in StarWind HyperConverged Appliance
More from ESX Virtualization
- How VMware HA Works?
- What is VMware Cluster?
- VMworld 2018
- Free Tools
- Install and Configure VMware vCSA 6.7
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