storage strategies – part 1

In follow-up to my previous article about bind mounts, here is the first in a series on storage strategies (while everything contained in this series is applicable to desktops and laptops, the main thrust will be towards servers). Today we’ll look at local/simple storage options (DAS – both the spinning and solid-state varieties).

The most basic form of utilizable storage is the direct-attached (or DAS) variety. In short, DAS covers any drives that are physically connected to a computer – hard drives, SSDs, etc.

Spinning disks, aka hard drives, are the most common form of DAS – and are extremely similar between consumer and professional levels (the only main differences are price^* and guaranteed reliability): they’re a very mature, stable technology, and, excepting recent problems in Thailand, have been pretty cheap for a long time.

Depending on the server, there will be anywhere from 2-12 (or more) disk slots. If the disks are sized equally, they can be either added to a RAID (a topic for a future post on fault-tolerance), or used individually.

A more recent alternative to hard drives have been solid-state storage. SSDs use flash memory – which can be more fault-tolerant than disk drives because there are no moving parts. While, as with all devices, there is a failure rate with flash storage, it [generally] fails more gracefully than a spinning disk, as individual cells of the flash will wear-out/become inaccessible, rather than a platter  physically crashing.

Pros:

• “traditional” storage, which makes installation simple
• storage performance can be easily isolated
• generally-speaking, it’s the fastest storage option
• cheapest storage option

Cons:

• if storage needs have been predicted too low, it can be costly and time-consuming to increase
• if storage needs have been predicted too high, a server could be “wasting” lots of space
• when failures happen, recovery can be a very time-consuming process

^{*_{There is an excellent question and answer on Server Fault that covers why costs of enterprise/professional storage are high, and I won’t rehash much of that information in this series.}}