[Need Help]isboot (iSCSI boot driver) version 0.2.1
aoyama at peach.ne.jp
Sun Jul 4 11:20:47 UTC 2010
>> Notes/Known Issues/Limitations:
>> FreeBSD can't use transfer length > 64KB.
> Since 8.0 FreeBSD can use any transfer lengths. 64K is a safety limit
> for CAM SIMs that do not report maximum transfer size. If your driver
> supports bigger transactions (and even if not), you should fill maxio
> field in XPT_PATH_INQ response.
I set maxio=1024*1024 in version 0.2.2. As a result, the request (each ccb)
have 256 blocks (128KB). I don't know why it is 128KB.
>> It seems CAM tag is used only 2 of 64 tags.
>> I don't know a reason, but MAXPHYS limit?
> How many concurrent requests you are submitting? If you are testing it
> with sequential read from file system - make sure you have sysctl
> vfs.read_max set high enough. MAXPHYS does not affects number of
> concurrent requests, only size of each one.
I used vfs.read_max=32 and run only one dd. Now vfs.read_max=2048.
I tried to run dd 4 times at background, then I got 4 x 30MB/s (read) and
4 x 21MB/s (write). Write is still slower than read, but it is enough.
I can see 1 or 2 tags when reading, around 10 tags when writing.
I guess that reading tag exists only for a short time.
(or my execution order is not good)
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