Terapix Star Formation Region IC 1396, © 2002 CFHT
Disk storage
by GTI - Updated July 3rd, 2003

Data are stored for processing on array disks (RAID). For security, the array disk will be configured as RAID level 4 or level 5, to avoid data loss in case of disk failure. Big files (images) would rather go on RAID level 4, small files would rather go on RAID level 5.

Loading the array with the contents of a full RUN [about 5 tera-pixels] could take a long time (see "numbers to keep an eye on" document). Data will be red many times (about 10 times each, and that makes tape download into a big buffer unefficient).

To date, there are (chronological order of install) :
-  RAID bay containing 8 * 36 gigas disks (= 245 gigas). The bay has its own RAID controller with 3 disk channels, each channel linking 2 or 3 disks, and has 64 Mega of cache memory. I/O ratio is expected to be around 30 megas/sec. The RAID controller SUPRA is from SYRED Data Systems. The device is from Advanced France Composants. NOTE : these device was first filled with 9 gigas disks.
-  RAID bay containing 8 * 18 gigas disks (= 120 gigas) very similar to the previous one except disk size. Configured as RAID level 5, with 64 Mega of cache memory.
-  RAID bay from TRANSTEC company - model 5200, containing 24 disks, SCA connector, 50 gigas bytes per disks, using 2 redundant controllers CRD-5640 from CMD Technology. There are 2 disk channels and 2 host channels. The configuration is : 3 RAID set of 8 disks each (= 3 * 340 gigas). Each set has 4 disks on each disk channel.
-  RAID bay containing 8 * 73 gigas disks (= 498 gigas), hotswapable. The bay has its own RAID controller with 3 disk channels, each channel linking 2 or 3 disks, and has 64 Mega of cache memory. I/O ratio is expected to be around 30 megas/sec. The RAID controller SUPRA is from SYRED Data Systems. The device is from Advanced France Composants.
-  RAID bay containing 8 * 81.9 gigas disks (= 556 gigas), hotswapable. The bay has its own RAID controller with 4 IDE disk channels, each channel linking 2 disks, and has 64 Mega of cache memory. This device is the cheapest by far, due to low prices for IDE disks, plus slow disks (spining at 5400 rpm). NOTE : due to huge file system, the volume is split into 2 partitions (NFS limits at 512 Megas).
-  RAID bay containing 16 * 81.9 gigas disks (= 1100 gigas), hotswapable. The bay has its own RAID controller with 8 SCSI disk channels, each channel linking 2 disks: NOTE that each IDE disk has its own IDE-SCSI adapter that allow an IDE to be on a SCSI channel. There are 2 RAID set of 8 disks each. There is 64 Mega of cache memory. This device is the cheapest by far, due to low prices for IDE disks, plus slow disks (spining at 5400 rpm). NOTE : due to huge file system, the volume is split into 2 partitions (NFS limits at 512 Megas).

Also, 4 simple disks, 36 gigas each (= 140 gigas) are available for users.

Total disk space : about 3500 gigas bytes (simple disk not included)


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