Sunday, April 15, 2012

Fastest Ext4 Options

When I got a new external hard drive for storing mp3s, recorded TV shows, etc, I wanted to know how to set it up most optimally (using the ext4 filesystem). I ended up following Luca Spiller's Ext4 Options for a Media Drive for the most part, but with a few tweaks:

Formatting the Drive

After plugging in the hard drive and running sudo fdisk -l to check what name the OS had assigned it (/dev/sdb1), I formatted the drive with the following options: -m 0 to create no extra room for root (I don't intend to use it as a boot drive); and -L bb to assign it a label of bb (so I can reference it by label in my /etc/fstab):

sudo mkfs.ext4 -m 0 -L bb /dev/sdb1
Configuring the Drive Options

Then I updated my /etc/fstab configuration with an entry for the new drive. Beyond the filesystem permission options of user, rw, exec, and suid (the order of which is significant), and the noauto option (to ignore the drive when booting), I added some options that make writing data less safe — but faster. Use man mount to get a brief description of these and all other possible options:

LABEL=bb /mnt/bb ext4 user,rw,exec,suid,noauto,noatime,nobh,nobarrier,commit=60,data=writeback,journal_async_commit 0 0

If this was an internal hard drive, or one that I intended to have connected at all times, I would have skipped the permissions and noauto options (so as to use the default permissions and allow it to auto-mount at boot time), and would have just specified the performance options:

LABEL=bb /mnt/bb ext4 noatime,nobh,nobarrier,commit=60,data=writeback,journal_async_commit 0 2
Creating the Drive Mount Point

In /etc/fstab I had configured the drive's mount point as /mnt/bb, so I created it and set its owner to myself (so I could mount the drive as a regular user, since I had included the user option in the /etc/fstab config):

sudo mkdir /mnt/bb && sudo chown justin:justin /mnt/bb
Mounting the Drive

Now whenever I plug in the drive, I can mount it as a regular user; either via its label:

mount -L bb

Or via its mount point:

mount /mnt/bb

Jetty 6 HTTPS Redirects

Another Jetty 6 trick I have had to use several times is patching it to enable redirects with the correct URL scheme when proxyied via HTTP behind a webserver using SSL. Because the connection between the webserver and jetty is just plain HTTP (without SSL), jetty will send the redirect with a plain http scheme:


But when the webserver is using SSL, what I really want is for it to send the redirect with an https scheme:


X-Forwarded- Headers

As described in jetty's reverse proxy docs, by setting the forwarded property in jetty's connector configuration, you can get jetty to use the server name/port and remote client IP-address from the X-Forwarded-Host and X-Forwarded-For headers that apache's mod_proxy includes automatically.

One header that mod_proxy does not include automatically, however, is X-Forwarded-Proto. You have to add that manually, via the RequestHeader directive in your apache config (wherever you included the ProxyPass directive that forwards requests to jetty):

ProxyPass http://localhost:8080/ ProxyPassReverse http://localhost:8080/ RequestHeader set X-Forwarded-Proto "https"

Patching Jetty 6

For jetty 7/8, that would be sufficient. With the above configuration, they'll send the correct redirects. But jetty 6 doesn't use the X-Forwarded-Proto header, so you have to create your own connector class to handle it. This is what I've done (for the nio connectors):

package com.pitchstone.lib.jetty; import; import; import org.mortbay.jetty.HttpFields; import org.mortbay.jetty.Request; import org.mortbay.jetty.nio.SelectChannelConnector; /** * Jetty nio connector. * Adds the ability to use the 'X-Forwarded-Proto' header * to set the request 'scheme' property. */ public class NioConnector extends SelectChannelConnector { private String _forwardedProtoHeader = "X-Forwarded-Proto"; public NioConnector() { super(); } // AbstractConnector protected void checkForwardedHeaders(EndPoint endpoint, Request request) throws IOException { super.checkForwardedHeaders(endpoint, request); HttpFields httpFields = request.getConnection().getRequestFields(); String forwardedProto = httpFields.getStringField(getForwardedProtoHeader()); forwardedProto = getLeftMostValue(forwardedProto); if ("http".equals(forwardedProto) || "https".equals(forwardedProto)) request.setScheme(forwardedProto); } // impl public String getForwardedProtoHeader() { return _forwardedProtoHeader; } public void setForwardedProtoHeader(String x) { _forwardedProtoHeader = x; } }

To use it, compile it, jar it up, and add the jar to jetty's lib/ext directory (/usr/share/jetty/lib/ext by default under ubuntu/debian). Then configure jetty.xml to use it, replacing org.mortbay.jetty.nio.SelectChannelConnector with this custom version:

<Call name="addConnector"> <Arg> <New class="org.mortbay.jetty.nio.SelectChannelConnector"> <New class="com.pitchstone.lib.jetty.NioConnector"> <Set name="host"><SystemProperty name="" /></Set> ... <Set name="forwarded">true</Set> </New> </Arg> </Call>

With that configuration and patch in place, jetty will now send redirects with the https scheme. It also will map these X-Forwarded-For headers to the ServletRequest API like so:

HeaderServletRequest Method