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disk Archives - AWS Managed Services by Anchor

Noop I/O scheduling with SSD storage

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Solid State Drives (SSDs) are not new in the server world, but they’re seen a somewhat limited takeup due to their high cost per gigabyte of storage. This has been changing as prices continue to drop, and we’re now at the point where SSDs represent a viable option for primary storage of high-value data that is read and written heavily. While SSDs are a drop-in replacement for traditional hard drives (HDDs) when it comes to servers, their behaviour and performance characteristics are fundamentally different. This means that the disk-access scheduling algorithms that we’ve developed over time, originally designed for rotational media, simply don’t work for SSDs. We recently observed some interesting behaviour as a result of changing disk access schedulers, which we thought we’d share with you here. The difference…

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VMware ESX Guest Disk IO

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Knowing the state of your disk IO latency in VMware ESX can help you pre-empt performance & capacity issues before the occur. There are a few guidelines you should keep in mind. These notes are directed towards people using directly attached storage. Write latency should be 0, because you have that fancy battery backed controller caching writes, right? Read latency should be under 8ms. Use the smallest stripe size possible for your RAID array setting. This helps keep random IO performance acceptable at the cost of some sequential performance. Do not virtualise very heavy random IO workloads on shared arrays, other guest VMs wont like you for it. Unless you have a very compelling reason not too, use RAID 10. Some other notes, specific to Linux guests are: Mount file…

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