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\section{Horde Hardware Requirements}
You can get a general sense for the hardware requirements of Horde by looking at the Deployments\footnote{http://example.com/index.php?page=Deployments} page.

Here are some general guidelines for determining the number of hard disk drives required for a given I/O load.  This information is probably more useful for email server administrators than Horde administrators because Horde is generally not I/O bound.

\subsection{Determining disk drives if you know the IOPS required}
If you can make an estimate of how many I/O's Per Second (IOPS) you need you can determine how many disks you'll need as RAID10 and how many disks you'll need as RAID5.

Generally, a single disk drive can do this many IOPS per disk:

\begin{quote}
15k rpm: 180-210 IOPS\newline
10k rpm: 130-150 IOPS\newline
7200 rpm: 80-100 IOPS\newline
5400 rpm: 50-80 IOPS\newline
\end{quote}

\newline
In a mirrored configuration:\begin{quote}
Disk IOPS = Read IOPS + (2 * Write IOPS)\newline
\end{quote}

\newline
In a parity (RAID5) configuration:\begin{quote}
Disk IOPS = Read IOPS + (4 * Write IOPS)\newline
\end{quote}

\newline
\subsection{Example calculations}
Now let's look at an example.  If you estimate that you need to support 40 Read IOPS (40 reads/sec) and 80 Write IOPS (80 writes/sec).

If you want to use a mirrored configuration of drives:

\begin{quote}
Disk IOPS = Read IOPS + (2 * Write IOPS) = 40r/s + (2 * 80w/s) = 200 Disk IOPSUsing 7200 rpm drives, you need: 200 / 50 = 4 disk drives\newline
Using 10k rpm drives, you need: 200 / 130 = 2 disk drives (always round up)\newline
\end{quote}

\newline
If you want to use a parity (RAID5) configuration of drives:\begin{quote}
Disk IOPS = Read IOPS + (4 * Write IOPS) = 40r/s + (4 * 80w/s) = 360 Disk IOPSUsing 7200 rpm drives, you need: 360 / 50 = 8 disk drives (always round up)\newline
Using 10k rpm drives, you need: 360 / 130 = 3 disk drives\newline
\end{quote}

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