olson@anchor.esd.sgi.com (Dave Olson) (02/28/91)
In <HARAKI.91Feb27105332@fermi.rc.m-kasei.co.jp> haraki@fermi.rc.m-kasei.co.jp (Susumu Haraki 3844) writes: | In article <1991Feb25.045950.17710@odin.corp.sgi.com> olson@anchor.esd.sgi.com (Dave Olson) writes: | <I don't know where you got your info, but even the slowest M-O | <drive I saw (an old sony) wrote at 100Kbytes/sec WITHOUT pre-erasing. | On DOS environment,Drives must updates FAT and directry. | And most of case,they are located most inner area. | Do you know the seeking speed of MO drives? | In addition to, an old sony drive are as fast as New one. I didn't see any mention of DOS, I was talking about real computers and OS's :-). The very first sony c501 I had for eval was definitely slower than newer ones; most likely a firmware fix. | <Current Sony, Ricoh, and Maxtor M-O's all write at 250-300Kbytes/s | <(at least) without pre-erasure. | Definitely NO!! | Because most of drives use three passes method in writing mode.(Except | old Sony drives[NWP-539S 2.05] ) | I don't check New Sony drive yet ;-< | (Erase,Write & Verify) I can only tell you that on standard out of the box SGI 4D25's, running IRIX 3.3, that I have measured these values, both through the filesystem and direct to the disk, both with software timers, and SCSI analyzers. You may not like it, but that is life. Zcav on the Tahiti helps, but not all that much (~ 10% improvement, by vague recollection), since the current Tahiti's spin at the same speed (2200?) for both media types (older ones spun at 1800 for non-ZCAV) My tests were typically writing and reading 16-32 Mbytes, with i/o sizes from 8K to 256Kbytes. The 600Kb read/250Kb write is at large block sizes (128Kb), and it does drop off at lower block sizes. As I recall, it was down to 400 Kb read, 150 Kb write at 16Kbytes per i/o, but this was some time ago, and I don't have the numbers handy at the moment. | <The next generation of drives | <will not require erase before write, so write speeds should be | <500-600 Kbytes/sec or more, which matches current read speed. | Yes. But including seeking time, the speed will be less than 500Kbytes/sec. | The heads of drives are too heavy to move quickly. True, seeking is somewhat slow, but even the current Tahiti is 35ms avg 1/3 stroke seek. Also, remember that reasonable designed OS's have file systems that can write large contiguous files, and therefore (for these types of files) seek time is not much of an issue. Using them as the main disk in a multi-user system would not be appropriate... -- Dave Olson Life would be so much easier if we could just look at the source code.
hue@island.COM (Pond Scum) (03/06/91)
In article <1991Feb25.045950.17710@odin.corp.sgi.com> olson@anchor.esd.sgi.com (Dave Olson) writes: >In <3721@island.COM> hue@island.COM (Pond Scum) writes: >| SCSI Magneto-Optical drives typically write around 70k bytes/sec. In order >I don't know where you got your info, but even the slowest M-O >drive I saw (an old sony) wrote at 100Kbytes/sec WITHOUT pre-erasing. garbonzo% time dd if=/dev/zero of=spud bs=256k count=20 20+0 records in 20+0 records out 0.0u 1.3s 1:02 2% 0+440k 6+652io 1pf+0w garbonzo% dc 256 1024 20 * * p 5242880 62 / p 84562 garbonzo% Vendor: SONY Product: SMO-C501-00 Rev. Level: 2.07 Formatted in ISO mode So what I really see is 82k bytes/sec, over 3X slower than you say it should be (70k might have been on a SPARCstation 1). The machine is a SPARCstation 2, SunOS4.1.1, Delta Microsystems smo driver, 1k byte/sector media. Do you think this drive has ancient firmware? We've bought three in the last few months (from Delta Microsystems and Artecon) and they all perform about the same. -Jonathan hue@island.COM
billbr@xstor.com (Bill Brothers) (03/07/91)
In article <3721@island.COM] hue@island.COM (Pond Scum) writes: ]In article <1991Feb13.134708.3440@news.larc.nasa.gov> kristi@arbs1.larc.nasa.gov (Kristi Skeens) writes: ]> ]>I am seeking advice/recommendations for an optical disk storage system to connect to a PC. The disk will be hooked up to a system that will be retrieving atmospheric measurements in real-time, therefore, fast writing speed is a must. ]>I know very little about optical systems, so any information would be helpful. ] ]SCSI Magneto-Optical drives typically write around 70k bytes/sec. In order ]to speed up writes, you have to keep the unused blocks on the disk in the ]erased state. If you do that, you can suppress the pre-erase pass during ]writes and will see something around 200K bytes/sec. I doubt any vendor ]can supply a driver which does what I just described, so you'll probably ]have to write your own. ] ] ]-Jonathan hue@island.COM You might be quite surprised at what some subsystem folks do... Bill Brothers Storage Dimensions, Inc. billbr@xstor.COM