Hardware Management - Deploying and Managing a Cloud Infrastructure - page 240

The type of file system that will be used has to complement the different technologies used
in the different storage tiers. Some of them are more suited to tape storage, for example, while
some excel when used with the much faster SSD.
EXT EXT stands for Extended File System. It was the first file system that was specifically
created for the Linux kernel. It was inspired by the Unix File System (UFS) and its idea of
metadata structure. EXT has gone through several revisions, the latest being EXT4. Table 8.1
presents some stats and figures for EXT evolution.

TABLE 8.1 EXT revisions

Max
volume
size

Filename
length EXT revision Introduced File allocation Max file size

EXT2 January 1993 Bitmap (free

space), table
(metadata)

32 TB 2 TB 255 bytes

EXT3 (unlike EXT2,
offers journaling)

November 2001 Bitmap (free

space), table
(metadata)

32 TB 2 TB 255 bytes

EXT4 (unlike EXT3,
offers: extents
for up to 128 MB
of contiguous
space, enhanced
subdirectory
limits, delayed
allocation to prevent
fragmentation)

October 2008 Extents/

bitmap

1 EB 16 TB

(4 KB block
system)

255 bytes

VMFS VMFS stands for Virtual Machine File System. VMFS is cluster file system developed
by VMware for use with its ESX Server and vSphere (a server virtualization suite). VMFS was
initially developed to store virtual machine disk images and snapshots. In VMFS, multiple
servers can read/write the same file system simultaneously, while individual virtual machine
files are locked. The size of VMFS volumes can be logically and nondestructively increased
(nondestructive to written data). The volume size can be increased by spanning multiple vol-
umes together. The features are as follows:

Optimizes virtual machine I/O with adjustable volume, disk, file, and block size.

■

Allows simultaneous access by multiple ESX servers by implementing per-file
locking.

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Adds or deletes hosts without disrupting other hosts.

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