Computer data storage - Some glossary
|Computer data storage|
|This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)|
DAS (Direct Attached Storage) - storage not physically in a host, but connected directly to just it (via SAS, SCSI, Fibre Channel, eSATA or such), May easily be faster than networking.
NAS (Network Attached Storage) - Storage attached via a (local area) network. Can refer to simple file sharing (SMB, NFS and such), to specific applicances.
SAN (Storage Area Network) - similar to NAS, but more specifically geared to be a centralized, dedicated storage service for a network of computers. (More of a service, while NAS is more of an appliance). SAN implementations often refer to larger-scale consolidated things.
iSCSI - effectively one implementation of NAS (and arguably SAN), with the largest difference being that it looks like a block device rather than a remote share.
- S.M.A.R.T.: Self-Monitoring Analysis and Report Technology, meant to monitor drive health and warn about imminent failure.
- (Compliance with this standard possibly seems to vary per manufacturer, and also probably somewhat per drive design)(verify)
- see also Computer data storage - Reading SMART reports
- Command queueing refers to planning an order of read and/or write commands order so that head position and rotational position are taken into account.
- In the best case a series of operations finishes faster, in the worst case it makes no difference and the overhead (fairly little for NCQ, while for TCQ it depends somewhat on the implementation/technology) makes things a little slower. The practical value of command queueing depends largely on the average and worst case influence.
- TCQ: Tagged Command Queueing: Done by the driver (verify)
- NCQ: Native Command Queueing: Done by the drive (SATA feature, optional?(verify)).