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Ares Disks

Ares has five internal 3.5 inch hard disk drives.

Ares boots up from a 36.4 GB SCSI hard disk, and this disk has two primary partitions and one logical:

Disk /dev/sda: 36.4 GB, 36420075008 bytes
255 heads, 63 sectors/track, 4427 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        4244    34089898+  83  Linux
/dev/sda2            4245        4427     1469947+   5  Extended
/dev/sda5            4245        4427     1469916   82  Linux swap / Solaris

Partition 1 is the / device, while partition 3 is swap space.

Ares also has four IDE disks that form three RAID 5 sets. The partition table of each disk is:

Disk /dev/hde: 203.9 GB, 203928109056 bytes
255 heads, 63 sectors/track, 24792 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hde1               1        1703    13679316   fd  Linux raid autodetect
/dev/hde2            1704        7783    48837600   fd  Linux raid autodetect
/dev/hde3            7784       24792   136624792+  fd  Linux raid autodetect

Note that although all four disks were originally 203.9 GB in size, one disk recently failed and needed to be replaced. It was replaced with a 250.0 GB drive which has the same partition table. There are three further 250.0 GB drives to be used as cold spares in case further drives fail.

We use mdadm to make our RAID devices on ares, and /etc/mdadm/mdadm.conf is:

DEVICE /dev/hd[efgh][123]
ARRAY /dev/md0 devices=/dev/hde1,/dev/hdf1,/dev/hdg1,/dev/hdh1
ARRAY /dev/md1 devices=/dev/hde2,/dev/hdf2,/dev/hdg2,/dev/hdh2
ARRAY /dev/md2 devices=/dev/hde3,/dev/hdf3,/dev/hdg3,/dev/hdh3

The md0 array is mounted as /var for 39 GB storage space. /var is used to store the telescope livepage databases, the system level web pages, all log files, and all user email.

The md1 array is mounted as /home for 138 GB storage space.

The md2 array is mounted as /data for 385 GB storage space.

External Drives - /data_removable/

Ares now has two external disks (USB 2.0) as a RAID1 array, mounted as /data_removable. These have not been permanently added to the fstab because of potential issues with the device names given out at the boot. To mount the /data_removable array you need to be logged in as root and then issue the following commands.

dmesg

Check the output of dmesg for mention of the removable drives. There should be two messages whch read something like SCSI device sdb: 1953525168 512-byte hdwr sectors (1000205 MB). The device ids should be sdb, sdc or sdd. Note which two have been assigned to the two disks and issue the command

mdadm -A /dev/md7 /dev/sdb1 /dev/sdc1

Replacing sdb, sdc with the ids from dmesg. Lastly,

mount -t xfs /dev/md7 /data_removable

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Page last modified on March 12, 2010, at 05:05 AM