# Stardog 7 HA cluster

**URL:** <https://community.stardog.com/t/stardog-7-ha-cluster/1854>\
**Category:** Support\
**Created:** [August 27, 2019, 8:49pm UTC](https://community.stardog.com/t/stardog-7-ha-cluster/1854 "2019-08-27T20:49:23Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![zachary.whitley](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/zachary.whitley/32/94_2.png) [@zachary.whitley](https://community.stardog.com/u/zachary.whitley)\
**Post date:** [August 27, 2019, 8:49pm UTC](https://community.stardog.com/t/stardog-7-ha-cluster/1854/1 "2019-08-27T20:49:24Z")

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I read something in the blog about Stardog 7 that piqued my curiosity

> Write throughput for single nodes is faster; but cluster writes are even faster still. Stardog 7 was designed specifically for our horizontally scalable cluster: thus, it can handle many simultaneous clients all writing at once without any of them blocking one another. Stardog 7’s new concurrent write perf improvements really show up in HA Cluster usage, which is the case that really counts for the enterprise.

I'm just a little curious about what type of scalability you're supporting. So you can now horizontally scale writes? What kind of consistency is there? I'm guessing that the data still needs to be able to fit onto a single machine and that you're not doing any kind of sharding....yet. 🙂

It all sounds very cool.

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**Author:** ![scott](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/scott/32/497_2.png) [@scott](https://community.stardog.com/u/scott)\
**Post date:** [August 27, 2019, 9:13pm UTC](https://community.stardog.com/t/stardog-7-ha-cluster/1854/2 "2019-08-27T21:13:58Z")

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Hi!

You are correct that Stardog 7 is not sharding(yet!), so data still needs to fit on a single machine. It also has the same level of consistency guarantees as all our previous versions, we're just using a different system to get there.

The big difference between Stardog 7 and previous versions is that it uses a non-blocking transactional storage engine under the covers( a high-level overview can be found at [Mastiff Storage Engine | Stardog](https://www.stardog.com/blog/mastiff-storage-engine/)). This means that transactions no longer block each other when writing data, which is the main driver of the large performance increases we see when running in clusters.

It also means that our transactional isolation level is a bit different--"Snapshot Isolation" instead of the previous "Read Committed". In practice this shouldn't make much difference (if you were assuming Read Committed before, you can continue to assume that without any ill effects).

Cheers!

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**Author:** ![zachary.whitley](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/zachary.whitley/32/94_2.png) [@zachary.whitley](https://community.stardog.com/u/zachary.whitley)\
**Post date:** [September 10, 2019, 9:16pm UTC](https://community.stardog.com/t/stardog-7-ha-cluster/1854/3 "2019-09-10T21:16:26Z")

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Closed on September 10, 2019, 9:16pm UTC

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