Flash based I/O accelerators for enterprises

Flash is an inexpensive and fast cache for servers. There are many solutions that manage flash and offer system-wide or application-specific acceleration. Major solutions are as follows:

  1. Sandisk FlashSoft
  2. Intel Cache Accelerator Software
  3. EMC XtremSW
  4. NetApp FlashCache
  5. LSI Nytro
  6. FusionIO

Features

  • These solutions cache disk blocks and uses flash as the primary tier of storage.
  • Since flash is way faster than disk, I/O speed up could reach 2x- 20x.
  • These solutions are pure s/w, s/w+h/w, stay in kernel and work at driver level
  • Intel CAS can accelerate selected applications on a system
  • There is no major differentiators among these solutions, except price 🙂
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Openstack swift: EADDRNOTAVAIL error

Problem

swift-bench keeps EADDRNOTAVAIL error with a highly concurrency setting and multiple swift-bench clients.

Setup

Ubuntu 13, Swift single machine installation (refer SAIO), swift-client runs local with no-proxy mode.

Solution

  • EADDRNOTAVAIL stands for either unavailability of ephemeral ports and a known kernel bug.
  • Check your range of ports: $cat /proc/sys/net/ipv4/ip_local_port_range
  • swift-bench in no-proxy mode uses direct client class based on Python’s HTTPLib. I saw that code for object write and read did not have connection close call. So, I added that. Please refer swift/common/direct_client.py.
  • The kernel bug is based on usage of bind() call during a connection setup from client. swift-bench so not use bind. So this possibility is ruled out.
  • Swift administration guide advises of following setting:
The following settings should be in /etc/sysctl.conf:
# disable TIME_WAIT.. wait..
net.ipv4.tcp_tw_recycle=1
net.ipv4.tcp_tw_reuse=1# disable syn cookies
net.ipv4.tcp_syncookies = 0
To load the updated sysctl settings, run $sudo sysctl -p

The above mentioned solutions reduced the problem significantly. If there is a better solution, let me know.

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