eli@spdcc.COM (Steve Elias) (08/30/88)
there are two versions of the st251 -- one has 40ms access time, the other has 28ms access time. how does seagate do this? the 28ms version (mlc-1 marked on drive) does indeed show an access time of 28ms when run through various disk test programs. but! its track to track seek time seems to be much slower than other 28ms drives. the st251 seems much slower than other 28ms drives that i've used. any clues, folks? perhaps it has a slower data transfer time, too.
tissot@nicmad.UUCP (Kevin Tissot) (08/31/88)
In article <1741@spdcc.COM>, eli@spdcc.COM (Steve Elias) writes: > there are two versions of the st251 -- one has 40ms access time, > the other has 28ms access time. > > how does seagate do this? the 28ms version (mlc-1 marked on drive) > does indeed show an access time of 28ms when run through various > disk test programs. but! its track to track seek time seems to > be much slower than other 28ms drives. Most drives in the 28ms and below range rely on voice coil actuators for positioning the heads. Seagate is the only vendor (that I know of) which gets this kind of speed from stepper motor drives. Seems they do some tricky stuff to do this, which in my experience makes the drives much more sensitive to temperature variations and mounting configuration. Result: probably the least expensive drive in this performance category, but you take your chances with data reliability. The choice is up to you... -- =============================================================================== Kevin Tissot {ucbvax,harvard,rutgers}!uwvax!nicmad!tissot ---------------------> {att,decvax,rolls}!nicmad!tissot ===============================================================================
haugj@pigs.UUCP (Joe Bob Willie) (08/31/88)
In article <1741@spdcc.COM> eli@spdcc.UUCP (Steve Elias) writes: >the st251 seems much slower than other 28ms drives that i've used. >any clues, folks? perhaps it has a slower data transfer time, too. track-to-track time includes settling time, which may be higher on the 28ms drive. average access time is 1/3 stroke time and only includes one settling time. so it is possible for the settling time to be higher on a `faster' drive and still have a lower 1/3 stroke time. i suspect such a drive is slower in reality because many small seeks would cause the settling time to become a larger and larger factor. the data transfer TIME is determined by the interleave factor and controller, etc. the data transfer RATE, which depends on the drive logic (pete holz{man,berg} (sp) is i believe the resident disk hardware guru around here) is fixed by the rotational speed of the disk and the amount of data on each track. -- =-=-=-=-=-=-=-The Beach Bum at The Big "D" Home for Wayward Hackers-=-=-=-=-=-= Very Long Address: John.F.Haugh@rpp386.dallas.tx.us Very Short Address: jfh@rpp386 "ANSI C: Just say no" -- Me
pjh@mccc.UUCP (Pete Holsberg) (09/02/88)
In article <383@pigs.UUCP> haugj@pigs.UUCP (Joe Bob Willie) writes:
...(pete holz{man,berg} (sp) is i believe the resident disk
...hardware guru around here)
Close! Should have been (pete hol{zman,sberg}), and it's the "Z-man"
who is the expert. I just good at asking questions. :-)
Pete Holsberg UUCP: {...!rutgers!}princeton!mccc!pjh
Technology Division ...!att!jonlab!mccc!pjh
Mercer College CompuServe: 70240,334
1200 Old Trenton Road GEnie: PJHOLSBERG
Trenton, NJ 08690 Voice: 1-609-586-4800woodman@suvax1.UUCP (David Woodman) (09/02/88)
July 1988 Byte magazine did a review of 40meg AT drives (40ms or less) and the ST251 came in with a fair marking. Coretest (ver. 2.8) said the same thing. I am running unix (minix) on my st251, not a good idea. Disk intensive OS's or development will put a lot of wear into the stepper motor. I am going to add an st4051 which is a 40meg, voice coil (40ms) for the same price. So far, so good at 8 months of use. ------------------------------------------------------------------------------ David Woodman UUCP: ...!uw-entropy!dataio!suvax1!woodman Seattle University USNail: P.O. Box 23202, Seattle WA 98102 Phone: (206) 223-9470 ------------------------------------------------------------------------------