mccalpin@vax1.acs.udel.EDU (John D Mccalpin) (06/13/90)
I am looking to expand my mass storage on my Silicon Graphics Personal Iris, and I noticed that at least one vendor is finally shipping the Maxtor Tahiti 1.2 GB read/write optical system. The dealer-supplied specs include: 1.2 GB capacity (600 MB/side) and an access time of 35 ms. I am really far more concerned about write speeds. I have skipped on most other read/write opticals because of the abysmal performance in that regard. For example, my NeXT optical only managed about 25 kB/s on writes (though the reads were very fast). Since I intend to use it both for backups and for data storage, I don't want the thing tied up for several hours/day just for the backups! So does anyone have real data on the read and write performance of this unit? -- John D. McCalpin mccalpin@vax1.udel.edu Assistant Professor mccalpin@delocn.udel.edu College of Marine Studies, U. Del. mccalpin@scri1.scri.fsu.edu
rcb@ccpv1.cc.ncsu.edu (Randy Buckland) (06/14/90)
Directly from section 2.1 of the manual that comes with the drive: C/C format ZCAV format 512 bytes/sec 1024 bytes/sec 512 bytes/sec 1024 bytes/sec -------------------------------------------------------------- Cap. 297.6 Mb 326.4 Mb 464.7 Mb 511.3 Mb per side seek time average 35 msec 35 msec track 1 msec 1 msec max 70 msec 70 msec latency 13.6 msec (2200 rpm) Transfer rate from/to disk 6.78 Mbits/sec 10 Mbits/sec (6.78 Mbits/sec - 13.17 Mbits/sec) Scsi (async) 1.5 Mbytes/sec Scsi (sync) 4 Mbytes/sec MTBF 30,000 hours -- Randy Buckland North Carolina State University rcb@ccpv1.cc.ncsu.edu (919) 737-2517
olson@anchor.esd.sgi.com (Dave Olson) (06/14/90)
Organization: Silicon Graphics, Inc. mccalpin@vax1.acs.udel.EDU (John D Mccalpin) writes: | I am looking to expand my mass storage on my Silicon Graphics Personal | Iris, and I noticed that at least one vendor is finally shipping the | Maxtor Tahiti 1.2 GB read/write optical system. | The dealer-supplied specs include: 1.2 GB capacity (600 MB/side) and | an access time of 35 ms. | I am really far more concerned about write speeds. I have skipped on | most other read/write opticals because of the abysmal performance in | that regard. For example, my NeXT optical only managed about 25 kB/s | on writes (though the reads were very fast). Since I intend to use it | both for backups and for data storage, I don't want the thing tied | up for several hours/day just for the backups! | So does anyone have real data on the read and write performance of | this unit? Under IRIX 3.3, which is our first release that officially supports the Tahiti (software-wise), I can reach a maximum of 600 Kb/sec read and 310 Kb/sec writes. (IRIX 3.3 is NOT shipping yet, and I can't say for sure when it will be shipping.) This is when doing 256 Kb or larger i/o's to the raw device. Through file system, I get about 400 Kb/s reads (when using lbsize=65536 mount option) and about 200 Kb/s writes. This is with the ZCAV media and 512 byte sectors, and using the outermost (highest density) zone. The non-ZCAV media is about 30% slower, at least at the beginning of the drive. Also note that this is with the Rev E controller board. The Rev D board Tahiti controller had to handle some of the the block addressing in firmware, and the reads were not much slower, but the writes were about 1/3 slower (about 200 Kb/s max, about 150 Kb/s filesystem). The earlier manuals erroneously stated that the bus transfer rate was 2 Mb/sec max, while it is actually 1Mb/sec. The 2Mb/s number was projected for sync mode scsi, which the drive doesn't yet support. The earlier manuals also showed the non-ZCAV media spinning at 1800 and ZCAV at 2200 RPM; for rev D and later controllers, both are at 2200 RPM. Formatted capacity for the ZCAV media is ~909000 sectors per side; I've forgotten what it was for non-ZCAV, but it was around 600000. The IRIX 3.3 release typically bundles up filesystem writes into 64K chunks for large contiguous files, so earlier releases would probably be much slower. Without the lbsize mount option, the reads are typically done at 16K, and are much slower. Finally, note that you will want an external unit, since the drive MUST be kept below 42 deg C, and this is not possible with an internal drive in the PI or any of the other 4D series machines. For what it is worth, the HP drive (rumored to be from SONY) is only slightly slower in my measurements, but doesn't seem to work correctly unless IRIX is configured to not allow SCSI disconnects. I only had one for a couple of days, so I can't say much about it. -- Dave Olson Life would be so much easier if we could just look at the source code.
izumi@violet.berkeley.edu (Izumi Ohzawa) (06/14/90)
>mccalpin@vax1.acs.udel.EDU (John D Mccalpin) writes: > >| that regard. For example, my NeXT optical only managed about 25 kB/s >| on writes (though the reads were very fast). This should be more like 100 kbytes/sec for writes. For example, copying a 2.67 MB file (Webster Dictionary index file) to optical takes 25-28 secs consistently either from Browser, or via standard unix cp command. Izumi Ohzawa, izumi@violet.berkeley.edu