[nSLUG] overview DB and inn

Stephen Gregory nslug at kernelpanic.ca
Wed Mar 8 12:05:52 AST 2006


On Tue, Mar 07, 2006 at 04:36:20PM -0400, Jeff Warnica wrote:
> 
> Third, would be the actual devices on the market. You cant get (or only
> recently have been able to get) 15K SATA disks. Its hard to find SATA
> disks with >3 year warranty's.  This has to do with marketing, and
> legacy, but not really with technology.

Seagate and now Maxtor desktop SATA drives carry a 5 year
warranty. This does not make these drives suitable for a server.

There are physical differences between drives that are not part of the
SATA or SCSI spec but are matched to those specifications based on
intended use. (If I understand correctly this is what Jeff wrote.)
There are three broad classes of drives.

SCSI (and FC etc) server drives are designed for a constant reads and
writes of small files. These drives use better motors, bearings, and
the armature windings that move the read heads are bigger. SCSI does
handle mutltiple small read, writes, and seeks better then SATA with
NCQ. Both SATA and SCSI server drives are designed to tolerate more
heat.

SATA (and old IDE/ATA) server drives are designed for constant use
with larger files. These drives have better motors and bearings and
may have heavier armature windings. Examples of these drives are
Seagate/Maxtor's NR (near line) and MaxLine series. These drives are
being positioned as "fast backup" devices and would typically sit
between regular fast drives and a tape backup. These drives should
also do well in small office environments were disk use is typically
light.

SATA desktop drives are designed for infrequent reads and writes. Most
now have quiet bearings and motors. These drives will burn up under
heavy load.

For those of you wondering why there are still 36GB SCSI drives: it is
all about the operations per second. Some tasks, such as mail servers
and databases, are heavily dependent on ops per second. Ops/s depend
are the number of physical spindles in the raid array. A 36GB drive is
a spindle with a single platter and a single read head giving the
fastest ops/s possible. The bits are nice and big too so it should be
more reliable then a 100GB platter.


-- 
sg

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