Reflections on VDI Write-Cache Storage Alternatives.
It is quite common that the overall cost of implementing VDI-up is over 80% dependent on the shared storage cost, especially when dealing with instances of VDI one tenant. Const purchases of effectiveness based on the bulk storage acquisition, hindering the possibility of incremental growth. At the same time the scalability of short- and long-term system is largely related to the storage design that should be reviewed during implementation VDI lifecycle.
It is also easy view that traditional VDI implementations favor server hosts in a blade form factor at the high densities of users targeting. the design of the blade revolves centered to the shared storage and little space for alternatives such as cheap local disk arrays available with 1U servers called "pizza boxes".
Consider the design pizza box where local storage can take the load carrier for writing requirements Cache While the search for alternatives to reduce dependence on shared storage and cutting the implementation in all, we will ensure that.
- predictable scalability at a reasonable cost
- provisions for incremental growth
- universal design model is ready to scale
- requirements solid time are met
as a starting point, let's look Provisioning picture "standard" via Citrix Provisioning Server. with write caching on the target VM only the data necessary for VM to run is transmitted, saving valuable storage space and time by not requiring the entire image to download on VM. This approach provides excellent resilience with minimal network load. Write-cache partition can also be used as a home for the system page file, store persistent data that can survive across reboots for newspapers such events, dumps and Citrix Personal vDisk, etc.
Some design deltas when comparing shared vs. local storage:
- High Availability (HA) capabilities with combination VDI + Hypervisor + PVS are achieved both shared storage and internal
- Although it is easier to reach FT (fault Tolerance) in a shared storage environment by simple opposition, HA, most VDI implementations do not offer the FT capacity due to the prohibitive cost
- shared storage allows for live VM migration of individual virtual machines is useful for maintenance on the fly hardware and rebalancing resources. However, there are practical limits when migrating large numbers of virtual machines in a typical VDI implementation
- Local storage design includes provisions for planned VM migrations can be accomplished by "bleeding" users to other physical hosts after disconnection and connection provided
- conservation persistent data on the shared storage is an easier task, although the local storage can provide backup and options as well
as an example of popular look 1U Dell and HP servers offers - R610 and DL360 G7 respectively available for around $ 10k- $ 16k
- 544 to 816GB of usable space ( 6 to 8x146GB, 15k drives, RAID 50 recommended)
- RAID controller storage quality with 512 to 1.024 MB cache
- 96-144 GB RAM
- Support more 100 users VDI single tenant (8GB of write cache, from 0.9 to 1.4 GB RAM, 100 Mbps per user) and about 100 0 VDI multi-tenant users or more
Although individual mileage may vary VDI implementations since all have identical requirements, we can clearly see the dramatic reduction potential costs at $ 100 / $ 0 per user in the host material costs, including storage. This contrasts the $ 1,000 cost per user equipment or more with common VDI implementations based entirely on expensive shared storage
In conclusion :.
Write-Cache unloading inexpensive high performance local storage provides linear scalability with provisions for incremental growth, affordable and sustainable. Independent accommodation in individual computer units offer excellent availability with less reliance on shared storage that can be optimized for storing data percistant and not trivialized as a dedicated write cache.
PS. To facilitate the adoption of local write cache and simplify disk management VDI simple technique described in the management of Citrix PVS Sheet Write-cache can be used.
PS # 2. " How about the IOP " - A frequently asked question in my presentations on this topic please take a look at the job. Thomas Berger: / blogs / 2011/12/01 / pvs-write-cache-to-local-disks-% E2% 80% 93-a-real-world-experience /
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