Subject: Disk upgrades on chemistry; disk striping
 
 In December 1997, a little more than a year ago, we doubled the size of /home
 from about 4 GB to about 8 GB. Predictably, a year later, a substantial
 amount of that space had been used.
 
 We could again have replaced the disk drive, going from a 9 GB drive to an 18
 GB drive, but that would have slowed down I/O (in general, the bigger the
 disk drive, the slower the I/O). Instead, we decided to add more 9 GB drives
 and make /home a stripeset of 2 9 GB drives. Striping (RAID-0) makes 2 or
 more drives appear as one logical drive (volume), and any file written to
 that logical volume will be split up into little chunks of data that will be
 written to the physical drives in a round-robin fashion. In other words,
 sufficiently large I/Os will be split up into pieces that are done in
 parallel. This method increases overall performance.
 
 Last fall, we added 3 more 9 GB drives to the chemistry server. One of those
 is owned by a research group. We purchased the Veritas Volume Manager
 software and reconfigured most of the disks last week (THU, Feb. 25 / FRI,
 Feb. 26).
 
 /home is now 16.2 GB large and is striped over 2 disks.
 
 /var/mail, the mail-spool (space where incoming email is stored) has been
 substantially increased to 4 GB and is also striped over 2 disks.
 
 /www, where all departmental web-pages reside, is now striped over 2 disks as
 well.
 
 Our total disk space on chemistry is now about 58 GB. Out of those 58 GB, 45
 GB are Wide Ultra Differential SCSI disks (40 MB/s peak transfer speed).