Purchasing S2D means buying all the Windows Server … Before sizing the storage devices, you should be aware about some limitations. The performance of cache memory is frequently measured in terms of a quantity called Hit ratio. NVMe + HDD. Similar to the above, the SSDs will accelerate reads and writes by caching both. This means that Hot Cold Data will be in your Performance Capacity Tier and the Cold Data will be in the rest of the Capacity Tier. Normally when deploying S2D, the disk types in the nodes are detected and the fastest disk (usually NVMe or SSD) is assigned to the cache, while the next fastest is used for the Performance Tier and the slowest being used in the Capacity Tier. With drives of all three types, the NVMe drives cache for both the SSDs and HDDs. I plan to improve the script next year by adding the support for disaggregated S2D deployment model and to add information such as the cache / capacity ratio and the reservation space. It is a large, persistent, real-time read and write cache. NVMe + SSD + HDD. We recommend limiting the total storage capacity per server to approximately 400 terabytes (TB). S2D is an alternative to traditional SAN or NAS arrays. There are over 1,000 components with the SDDC AQs.The fu… What happens in case of lack of cache? The cache should be sized to accommodate the working set of your applications and workloads, i.e. For environments with a variety of applications and workloads, some with stringent performance requirements and others requiring considerable storage capacity, you should go "hybrid" with either NVMe or SSDs caching for larger HDDs. You could also have 12 capacity drives, to 2 cache drives. Intel has a very thorough article that explains what happens when the workload data volume on a Storage Spaces Direct (S2D) Hyper-Converged Infrastructure (HCI) cluster starts to "spill over" to the capacity drives in a NVMe/SSD Cache with HDD Capacity for storage. No shared-SAS is supported. VSAN 6.2 - Cache to Capacity Ratio One of the integral component of VSAN storage subsystem is a Disk-group. The same is true in the case of drive failure in which case S2D self heals to ensure a proper balance. There is one additional, rather exotic option: to use drives of all three types. If all your drives are the same model, there is no cache. :D, Yeah, gotta love 'em! It's used to describe the capacity overhead that can be attributed to resiliency and will depend on which resiliency option you choose. TIP: Excellent NVMe PCIe AiC for lab setups that are Power Loss Protected: Intel SSD 750 Series, Intel SSD 750 Series Power Loss Protection: YES, These SSDs can be found on most auction sites with some being new and most being used. For example, if you had 8 storage drives and 4 cache drives, 2 disks would bind to each cache drive. 4 servers x 16 drives each x 2 TB each = 128 TB From this 128 TB in the storage pool, we set aside four drives, or 8 TB, so that in-place repairs can happen without any rush to replace drives after they fail. or IO throughput (we've done over 1 Tb/s! As with All-NVMe, there is no cache if all your drives are the same model. Click Create a new disk group. This deployment has total physical capacity, excluding cache. The binding between cache and capacity drives can have any ratio, from 1:1 up to 1:12 and beyond. In deployments with multiple types of drives, it is configured automatically to use all drives of the "fastest" type. Yes, you need to have multiple NVMe cards because 'cache tier' is always mirrored regardless of what redundancy level you chose for 'capacity tier', mirror or parity. A Disk-group in VSAN comprises of Cache Tier and Capacity Tier. We wanted to use some existing Dell R620 hardware to play with Storage Spaces Direct S2D in the lab. The current maximum size per storage pool is 4 petabyte (PB) (4,000 TB) for Windows Server 2019, or 1 petabyte for Windows Server 2016. So, we actually followed the configuration that we had laid out in Chapter #5 in the book and ran into the following issue: MediaType = Unspecified If we look into the cache, a lot of miss per second are registered especially on the high latency CSV. It assumes that the capacity tier will scale cache overwrites and endurance usage with its capacity growth The reality is that: Workload read write ratio and randomness 70% or higher random read workloads can make do with much less cache (800GB for larger hosts, 200GB for small ones). This guarantees an immediate, in-place, parallel repair can succeed after the failure of any drive, even before it is replaced. In deployments with multiple types of drives, it is configured automatically to use all drives of the "fastest" type. Always ask for an Intel SSD Toolbox snip of the drive's wear indicators to make sure there is enough life left in the unit for the thrashing it would get in a S2D lab! Reserve capacity For this to work, you need to set aside some extra capacity in the storage pool. S2D cache drives work by creating a ‘bind’ between storage drives and cache drives. We need to have One Cache drive and maximum of seven Capacity drives to form a disk group. Here is a previous post that has an outline of what we do along with links to quite a few other posts we've done on the topic: Hyper-V Virtualization 101: Hardware and Performance. For deployments with HDDs, a fair starting place is 10% of capacity – for example, if each server has 4 x 4 TB HDD = 16 TB of capacity, then 2 x 800 GB SSD = 1.6 TB of cache per server. You can think of this as giving the contents of a failed drive "somewhere to go" to be repaired. For a cache drive, re-create the disk group. Here are some starting points based on a 2U S2D node setup we would look at putting into production. Secondly, yo… The remaining drives are used for capacity. All NVMe. Every server must have at least two cache drives (the minimum required for redundancy). Because of this, it was always a good idea to keep an eye on how your cache was going, making sure things like Cache Hit Misses were low, and that your Write Cache wasn’t overallocated. You can also mix higher-endurance and lower-endurance NVMe models, and configure the former to cache writes for the latter (requires set-up). Oversizing cache enables you to add more capacity to an existing disk group without the need to increase the size of the cache. We recommend using the SSD tier to place your most performance-sensitive workloads on all-flash. But why Miss/sec can produce a high latency? Using NVMe together with SSDs, the NVMe will automatically cache writes to the SSDs. An advantage to using all-NVMe or all-SSD with no cache is that you get usable storage capacity from every drive. One thing to keep in mind when it comes to a 2U server with 12 front facing 3.5" drives along with four or more internally mounted 3.5" drives is their heat and available PCIe slots. Co-Author: SBS 2008 Blueprint Bookwww.s2d.rocks !Our Web SiteOur Cloud Service. Click OK. To achieve predictable and uniform sub-millisecond latency across random reads and writes to any data, or to achieve extremely high IOPS (we've done over six million!) SSD + HDD. We recommend making the number of capacity drives a multiple of the number of cache drives. For more information, check out Understanding the cache in Storage Spaces Direct. Device counts: cache 3 capacity 15 Binding ratio is even: 1:5 All disks are in InitializedAndB ound yet 3 other nodes report Device counts: cache 3 capacity 15 WARNING: Binding ratios are uneven Groups: 1:6 (1 total), 1:5 (1 total), 1:4 (1 total) All disks are in InitializedAndB ound All nodes are identical. Caching reads allows the HDDs to focus on writes. This results in a cache bind of 2:1. Flash caching devices must have high write endurance. No sponsorship or monies have been paid to MPECS Inc. for their review or mention. This topic provides guidance on how to choose drives for Storage Spaces Direct to meet your performance and capacity requirements. In this case, that's drives x each. ;), Philip Elder Microsoft High Availability MVPMPECS Inc. This means you can add cache drives or capacity drives independently, whenever you want. writing), PCIe: Peripheral Component Interconnect Express. of hits/total accesses We can improve Cache performance using higher cache block size, higher associativity, reduce miss rate, reduce miss penalty, and reduce the time to hit in the cache. Make sure the storage configuration for each S2D host is compatible (Image courtesy of Microsoft) Beginning Storage Spaces Direct Configuration The more storage capacity per server, the longer the time required to resync data after downtime or rebooting, such when applying software updates. NVMe + SSD. This provides NVMe-like write characteristics, while reads are served directly from the also-fast SSDs. Cache and capacity drives are required as part of the configuration. In addition, we recommend that servers, drives, host bus adapters, and network adapters have the Software-Defined Data Center (SDDC) Standard and/or Software-Defined Data Center (SDDC) Premium additional qualifications (AQs), as pictured below. Using all NVMe provides unmatched performance, including the most predictable low latency. There is no capacity "spent" on caching, which may be appealing at smaller scale. Configuration with HDDs only is not supported. Some Thoughts on the S2D Cache and the Upcoming Intel Optane DC Persistent Memory, IOPs performance on NVMe + HDD configuration with Windows Server 2016 and Storage Spaces Direct, Hyper-V Virtualization 101: Hardware and Performance, The new HCI industry record: 13.7 million IOPS with Windows Server 2019 and Intel® Optane™ DC persistent memory, EE Article: Some Hyper-V Hardware and Software Best Practices, EE Article: Practical Hyper-V Performance Expectations. Might have to raise this with Microsoft. For example, if you have 4 cache drives, you will experience more consistent performance with 8 capacity drives (1:2 ratio) than with 7 or 9. It uses built-in Windows features and tools to configure highly-available storage that crosses multiple nodes in a cluster. For more information, check out Understanding the cache in Storage Spaces Direct. Microsoft S2D does indeed have the potential to pool diverse storage into powerful systems but it costing a fraction of a SAN price is questionable. Plus, the additional drives could also place a constraint on the processors that are able to be installed also due to thermal restrictions. Storage Spaces Direct comes as the highest-tier Windows Server license. We discuss various vendor and manufacturer products and services here. We always try to have the right amount of cache in place for the workloads of today but also with the workloads of tomorrow across the solution's lifetime. If you mix higher-endurance and lower-endurance models, you can configure the former to cache writes for the latter (requires set-up). So, what do we do to make sure we don't shortchange ourselves on the cache? Being dyslexic has its challenges with them too. Each server has some cache drives plus sixteen 2 TB drives for capacity. Storage Spaces Direct features a built-in server-side cache. And Storage Spaces Direct (S2D) is no different today, especially in Hybrid (SSD+HDD) deployments. Select a flash device under cache tier and select 4 HDD/SSD devices under Capacity tier. For example, to repair from one drive failure (without immediately replacing it), you should set aside at least one drive’s worth of reserve capacity. Understanding the cache in Storage Spaces Direct, Understand the cache in Storage Spaces Direct, Storage Spaces Direct hardware requirements, Planning volumes in Storage Spaces Direct. The appeal is that you can create volumes on the SSDs, and volumes on the HDDs, side-by-side in the same cluster, all accelerated by NVMe. The NVMe drives will accelerate reads and writes by caching both. The former are exactly as in an "all-flash" deployment, and the latter are exactly as in the "hybrid" deployments described above. Secondly, in a 24 drive 2U chassis if we start off with four cache devices and lose one we still maintain a decent ratio of cache to capacity (1:6 with four versus 1:8 with three). That's the platform Microsoft set an IOPS record with set up with S2D and Intel Optane DC persistent memory: We have yet to see to see any type of compatibility matrix as far as the how/what/where Optane DC can be set up but one should be happening soon! Essentially, any workload data that needs to be shuffled over to the hard disk layer will suffer a performance hit and suffer it big time. It should be noted that they will probably be frightfully expensive with the value seen in online transaction setups where every microsecond counts. all the data they are actively reading and writing at any given time. This provides SSD-like write characteristics, and SSD-like read characteristics for frequently or recently read data. In the Manage tab, select vSAN > Disk Management and select the host that had the drive replaced. The cache ratio is 1:4 and its capacity is almost of 6,5% of the raw capacity. TIP: When looking to set up a S2D cluster we suggest running with a higher count smaller volume cache drive set versus just two larger capacity drives. We baseline our intended workloads using Performance Monitor (PerfMon). ), you should go "all-flash". Dynamic cache bindings ensure that the proper ratio of cache:capacity disks remain consistent for any configuration regardless of whether cache or capacity disks are added or removed. When you have NVMe in your storage configuration, Storage Spaces Direct automatically uses the NVMe device for the Caching Tier and the SSDs and HDDs for the Capacity Tier. It adjusts dynamically whenever drives are added or removed, such as when scaling up or after failures. For all-flash deployments, especially with very high endurance SSDs, it may be fair to start closer to 5% of capacity – for example, if each server has 24 x 1.2 TB SSD = 28.8 TB of capacity, then 2 x 750 GB NVMe = 1.5 TB of cache per server. We recommend using drives of the same model and firmware version whenever possible. Systems, components, devices, and drivers must be Windows Server 2016 Certified per the Windows Server Catalog. For one, we get a lot more bandwidth/performance out of three or four cache devices versus two. The solution I troubleshooted is composed of 2 SSD and 8 HDD per node. Caching writes absorbs bursts and allows writes to coalesce and be de-staged only as needed, in an artificially serialized manner that maximizes HDD IOPS and IO throughput. If you can't, carefully select drives that are as similar as possible. This allows writes to coalesce in cache and be de-staged only as needed, to reduce wear on the SSDs. However, the storage devices are bigger and bigger so 24 storage devices per node is enough (I have never seen a deployment with more than 16 storage devices for Storage Spaces Direct). Make sure to choose a solution that can take advantage of SSD drives to accelerate performanc… Some Thoughts on the S2D Cache and the Upcoming In... Server Storage: Never Use Solid-State Drives witho... Security: Direct Internet Connections for KVM over... 12x xTB HDD (some 2U platforms can do 16 3.5" drives), 4x 960GB Read/Write Endurance SATA SSD (Intel SSD D3-4610 as of this writing), 20x 960GB Light Endurance SATA SSD (Intel SSD D3-4510 as of this writing), Example 3 - Intel Optane AiC Cache and SATA SSD Capacity, 24x 960GB Light Endurance SATA SSD (Intel SSD D3-4510 as of this InitializedAndBound {48b3c541-6f8e-864d-88de-af3f4ed63f04} 6 = cache false 9 0 0 InitializedAndBound {00663d2f-abd6-0ffc-0d28-1b3d49773754} 7 = cache false 11 0 0 . In a setup where we would have either NVMe PCIe Add-in Cards (AiCs) or U.2 2.5" drives for cache and SATA SSDs for capacity the performance hit would not be as drastic but it would still be felt depending on workload IOPS demands. Broadberry S2D Hyper-Converged ... Capacity efficiency is the ratio of usable space to volume footprint. NVMe + SSD + HDD. This is conceptually like having two pools, with largely independent capacity management, failure and repair cycles, and so on. Storage Spaces Direct currently works with four types of drives: Storage Spaces Direct features a built-in server-side cache. Special thanks. Applies to: Windows Server 2019, Windows Server 2016. SBS, SMB, SME, Hyper-V Failover Clusters, Technology, System Builder Tips, views from the I.T. Device counts: cache 4 capacity 4 Binding ratio is even: 1:1 You can always add or remove cache drives later to adjust. We put in 2 x SSD Drives for the Cache (Journal) and 4 x SATA Drives for the Storage Pool. Windows Server 2016 can’t handle more than 26 storage devices so if you deploy your Operating System on two storage devices, 24 are available for Storage Spaces Direct. We discourage mixing-and-matching drives of the same type with sharply different performance or endurance characteristics (unless one is cache and th… Hit ratio = hit / (hit + miss) = no. First you can’t exceed 26 storage devices per node. When caching for hard disk drives (such as SSDs caching for HDDs), both reads and writes are cached. I’ve been deploying a few Storage Spaces Direct (S2D) clusters lately, and I noticed a slight mis-configuration that can occur on deployment. When caching for solid-state drives (such as NVMe caching for SSDs), only writes are cached. S2D automatically determinates the cache based on the type(s) of drives that are being cached for. The remaining drives are used for capacity. We are gearing up for a lab refresh when Intel releases the "R" code Intel Server Systems R2xxxWF series platforms hopefully sometime this year. We recommend setting aside the equivalent of one capacity drive per server, up to 4 drives, for in-place recovery. An SSD can support up to 50 times more I/O operations per second (IOPs) than a typical HDD. The same is true about so-called 'multi-resilient disks', you still have 'mirror' acknowledging writes, so need 2x of NVMe/SSD. I’d like to thanks Dave Kawula, Charbel Nemnom, Kristopher Turner and Ben Thomas. There is no cache size requirement beyond that. For workloads which require vast capacity and write infrequently, such as archival, backup targets, data warehouses or "cold" storage, you should combine a few SSDs for caching with many larger HDDs for capacity. RAID cards must support simple pass-through mode. In vCenter, select the host with the replaced cache drive. Example 2 - SATA SSD Cache and Capacity 4x 960GB Read/Write Endurance SATA SSD (Intel SSD D3-4610 as of this writing) 20x 960GB Light Endurance SATA SSD (Intel SSD D3 … The use of solid-state drives along with traditional spinning hard disk drives can significantly improve performance. It is a large, persistent, real-time read and write cache. A higher cache-to-capacity ratio eases future capacity growth. High endurance SSDs caching to low endurance SSDs is not advised. All SSD. An S2D storage solution also provides storage cache within memory, and storage tiering between different disk types like NVMe, SSD, and HDD. This provides NVMe-like write characteristics, and for frequently or recently read data, NVMe-like read characteristics too. Trenches, and more.

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