randy@ranhome.UUCP (Randy Horton) (05/31/86)
In article <150@percival.UUCP> nerd@percival.UUCP (Michael Galassi) writes: [deleted text] >Now for my question, does anyone have some good/bad experiences w/ the >WREN series of drives from CDC? Specificaly the WREN II series which >acomodates the ST506 standard (they say). If any CDC people are reading >this, feel free to reply, I have your multi-color glosies already though, >I just need info like prices and reliability figures (real ones that is). > >-- I have used a number of these drives, mostly in the 30Mb size. I have found them to be generally very good drives. They are relatively quiet and seem to be very reliable. There does seem to be one small problem that is particular to this model however. It seems that when you turn them off, sometimes the head gets stuck to the platter (that is the explanation an engineer gave me). When you turn them back on, they do not spin up, unless you give the computer a good whack! Now this only happens to some of them, and only some of the time. If you never turn off your computer, it will never be a problem. This also seems to happen less frequently if the drive is in a sidways position. Before I set it sideways, I often had to whack my machine to get the Wren to spin up, but the whacking never seemed to hurt anything. Now I leave my machine (a Unix box) on all of the time, and never have any trouble. Apart from the aforementioned problem, I have NEVER had a problem with a Wren, and I would actually reccomend them. (Randy Horton) allegra| hplabs | topaz |-!pyramid!ranhome!randy decwrl | -- (Randy Horton) allegra| hplabs | topaz |-!pyramid!ranhome!randy decwrl |
amr@rti-sel.UUCP (Alan Roberts) (06/02/86)
In article <191@ranhome.UUCP> randy@ranhome.UUCP (Randy Horton) writes: >[deleted text] >be very reliable. There does seem to be one small problem that is particular >to this model however. It seems that when you turn them off, sometimes the >head gets stuck to the platter (that is the explanation an engineer gave me). >When you turn them back on, they do not spin up, unless you give the computer >a good whack! This problem is known as "striction," I believe, and is a common problem with all brands of small hard disks, not just Wrens. It is more likely to happen as the drives get older, and is ultimately one of the factors that limits lifetime of the drive (assuming nothing else kills it first). As I understand it, when the head(s) on a hard disk land during power-off, they tend to polish the landing area. After some time, the landing surface fits so smoothly against the head that NO air remains between the two surfaces. The head then "sticks" to the surface with whatever force the ambient air pressure exerts. Its the same effect that makes gauge blocks stick. What happens when you next power up depends on the specifics of the spindle motor and head assembly. Either it holds the platter and keeps it from spinning, or the torque developed tears the head off the flexure! If its the former, then the "whack" will often dislodge the two. You'll know if its the latter, the sound of the loose head bouncing around will tip you. This "feature" of hard disks is the counter argument to always parking the heads over a landing zone and powering off the drive, a policy that I have heard recommended by most computer sales types. Always landing the heads, and in the same place, is probably going to hasten the day when they stick. I believe the best policy for your hard disk is to move the heads over a landing zone (in case of power failure), but leave the drive up, assuming that your environment is sufficiently cooled and your power is stable. -- Cheers, Alan Roberts Research Triangle Institute (decvax!mcnc!rti-sel!amr)