Merge pull request open-guides#128 from ehippy/patch-1

grammatical improvement

README.md

@@ -803,7 +803,7 @@ EBS
 
 ### EBS Gotchas and Limitations
 
--	❗EBS durability is reasonably good for a regular hardware drive (annual failure rate of [between 0.1% - 0.2%](http://aws.amazon.com/ebs/details/#availabilityanddurability)). On the other hand, that is very poor if you don’t have backups! By contrast, S3 durability is extremely high. *If you care about your data, back it up S3 with snapshots.*
+-	❗EBS durability is reasonably good for a regular hardware drive (annual failure rate of [between 0.1% - 0.2%](http://aws.amazon.com/ebs/details/#availabilityanddurability)). On the other hand, that is very poor if you don’t have backups! By contrast, S3 durability is extremely high. *If you care about your data, back it up to S3 with snapshots.*
 -	🔸EBS has an [**SLA**](http://aws.amazon.com/ec2/sla/) with **99.95%** uptime. See notes on high availability below.
 -	❗EBS volumes have a [**volume type**](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSVolumeTypes.html) indicating the physical storage type. The types called “standard” (**st1** or **sc1**) are actually old spinning-platter disks, which deliver only hundreds of IOPS — not what you want unless you’re really trying to cut costs. Modern SSD-based **gp2** or **io1** are typically the options you want.