![]() ![]() The introduction of ATS removed scaling limits via the removal of lock contention thus, moving the bottleneck down to the storage, where many traditional arrays had per-volume I/O queue limits. High intensity virtual machine operations such as boot storms, or virtual disk growth.Extremely dynamic environments-numerous provisioning and de-provisioning of VMs (e.g. ![]() The standard use cases benefiting the most from ATS include: Therefore, situations with large amounts of simultaneous virtual machine provisioning operations will see the most benefit. ATS allows for ESXi hosts to no longer queue metadata change requests, which consequently speeds up operations that previously had to wait for a lock. This behavior makes the metadata change process not only very efficient, but more importantly provides a mechanism for parallel metadata access while still maintaining data integrity and availability. With VAAI ATS, the lock granularity is reduced to a much smaller level of control (specific metadata segments, not an entire volume) for the VMFS that a given host needs to access. This behavior not only caused metadata lock queues but also prevented standard I/O to a volume from VMs on other ESXi hosts which were not currently holding the lock. In a cluster with multiple nodes, all metadata operations were serialized and hosts had to wait until whichever host, currently holding a lock, released that lock. #Datastore usage on disk alarm clearing .snapshot netbackup fullPrior to the introduction of VAAI ATS, VMFS used LUN-level locking via full SCSI-2 reservations to acquire exclusive metadata control for a VMFS volume. VMware resolved the first issue with the introduction of Atomic Test and Set (ATS), also called Hardware Assisted Locking. Per-volume queue limitations on the underlying array.This limit traditionally was due to two reasons: In the past a recommendation to use a larger number of smaller volumes was made for performance limitations that no longer exist. Using a smaller number of large volumes is generally a better idea today. The FlashArray supports far larger than that, but for ESXi, volumes should not be made larger than 64 TB due to the filesystem limit of VMFS. A common question when first provisioning storage on the FlashArray is what capacity should I be using for each volume? VMware VMFS supports up to a maximum size of 64 TB. ![]()
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