2048 byte/sector problems with kernel 2.4
Quoted 10 lines · Harvey Fishman
Quoted 4 lines · Alan Cox
Quoted 1 line
I also tried it with 2.2.18 there it works but it seems to be >utterly slow. I'm using kernel 2.4.2(XFS version to be precise).
M/O disks are slow. At a minimum make sure you are using a physical >block size of 2048 bytes when using 2048 byte media and plenty of memory to
Quoted 1 line
cache stuff when reading. Seek times on M/O media are pretty poor
Another thing making for the snailicity of MO drives is that writing is >a two pass operation. It is very like core memory; first you write the >spot to a known state, and then you write the data. So you have an average latency of 25 mS. for write operations and 8.33 mS. for read >operations. There WERE direct overwrite media for a while that would, in theory, be able to write the data directly, but a combination of high cost, >limited sources, and strong questions about the permanence of the recorded data severely limited the demand for these and I think that they have been withdrawn.
Harvey
No, direct overwrite disks are expensive, but they are still available. I do not know of any, and have not heard of any problems related to direct overwrite technology. For some reason M/O never really caught on in the US, and the high price of direct overwrite disks is what seems to be killing them off. I have a bunch I use for backup and have never had any problems.
Slow is a relative term. Compared to a Seagate X15? Yes, a M/O drive is probably slower. Compared to an 8X CD burner? No, my 640MB and 1.3GB M/O drives are quite a bit faster, particularly for random writes. For most applications, M/O is designed to compete with the latter, rather than the former.
People need to remember that M/O drives are meant to compete with CD-R or CD-RW as a moderate capacity, highly robust storage medium for archiving and backup. But it is somewhat annoying that 2.4.x doesn't (yet) support their 2K sector sizes correctly.
- John
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Quoted 6 lines
Quoted 6 lines
There WERE direct overwrite media for a while that would, in theory, be able to write the data directly, but a combination of high cost, >limited sources, and strong questions about the permanence of the recorded data severely limited the demand for these and I think that they have been withdrawn.
I have 2 OW disks and they work just fine. According to specs their reliability is the same as nornal MO disks.
Quoted 5 lines
No, direct overwrite disks are expensive, but they are still available. I do not know of any, and have not heard of any problems related to direct overwrite technology. For some reason M/O never really caught on in the US, and the high price of direct overwrite disks is what seems to be killing them off. I have a bunch I use for backup and have never had any problems.
RW CDs killed almost all removables.
And about 2KB sectors related problems, I confirm what I wrote in my previous
message: I have no problems. 640MB and 1.3GB both work fine here.
(kernel 2.4.3, old aic7xxx driver, adaptec 2930CU, Fujitsu GigaMO, PowerPC
750)
Bye.