AWS Storage Gateway User Guide
Sizing the Upload Buffer
Local Storage
Description
Gateway Type
the gateway uploads the data
to Amazon S3. Your gateway
uploads this buffer data over an
encrypted Secure Sockets Layer
(SSL) connection to AWS.
• Tape gateways
Cache storage
The cache storage acts as the
on-premises durable store for
data that is pending upload to
Amazon S3 from the upload
buffer. When your application
performs I/O on a volume or
tape, the gateway saves the
data to the cache storage for
low-latency access. When your
application requests data from
a volume or tape, the gateway
first checks the cache storage
for the data before downloading
the data from AWS.
• Cached volumes
• Tape gateways
• File gateways
Note
When you provision disks, we strongly recommend that you do not provision local disks for
the upload buffer and cache storage if they use the same physical resource (the same disk).
Underlying physical storage resources are represented as a data store in VMware. When you
deploy the gateway VM, you choose a data store on which to store the VM files. When you
provision a local disk (for example, to use as cache storage or upload buffer), you have the
option to store the virtual disk in the same data store as the VM or a different data store.
If you have more than one data store, we strongly recommend that you choose one data store
for the cache storage and another for the upload buffer. A data store that is backed by only one
underlying physical disk can lead to poor performance in some situations when it is used to back
both the cache storage and upload buffer. This is also true if the backup is a less-performant
RAID configuration such as RAID1.
After the initial configuration and deployment of your gateway, you can adjust the local storage by
adding or removing disks for an upload buffer. You can also add disks for cache storage.
Determining the Size of Upload Buffer to Allocate
You can determine the size of your upload buffer to allocate by using an upload buffer formula. We
strongly recommend that you allocate at least 150 GiB of upload buffer. If the formula returns a value
less than 150 GiB, use 150 GiB as the amount you allocate to the upload buffer. You can configure up to
2 TiB of upload buffer capacity for each gateway.
Note
For volume gateways, when the upload buffer reaches its capacity, your volume goes to PASS
THROUGH status. In this status, new data that your application writes is persisted locally but not
uploaded to AWS immediately. Thus, you cannot take new snapshots. When the upload buffer
capacity frees up, the volume goes through BOOTSTRAPPING status. In this status, any new
data that was persisted locally is uploaded to AWS. Finally, the volume returns to ACTIVE status.
Storage Gateway then resumes normal synchronization of the data stored locally with the copy
stored in AWS, and you can start taking new snapshots. For more information about volume
status, see
Understanding Volume Statuses and Transitions (p. 171)
.
For tape gateways, when the upload buffer reaches its capacity, your applications can continue
to read from and write data to your storage volumes. However, the tape gateway does not write
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