freebsd-performance Digest, Vol 4, Issue 7

Jin Guojun [DSD] j_guojun at
Wed Jun 18 15:42:16 PDT 2003

Petri Helenius wrote:

> > Recently, we tested software RAID via CCD and VINUM, and compared
> > them to adaptec 2xxx RAID controller. The performance is the same.
> > The CPU are Xeon 2.8 GHz, SuperMicro MB with ServerWork Chipset.
> > Seagate 3147xxxxLC drives.
> >
> > Problem is the write is slow for all of them, especially when multiple writes.
> >
> Write shouldn´t be too slow on RAID1. On RAID5 it depends on the implementation,
> how much overlapping it does and how much overlapping does your test have.

The problem is on RAID 1 (mirroring). This may not be the RAID issue,
but the SCSI drive and controller combination problem.
10 years ago, Seagate published Elite2 drive, which does not comply with SCSI
spec. It took me a quite time to diagnose it. What happened was Elite2 hold
SCSi bus for two period of cycles, then release the bus. This killed performance.

But this seems to have different problem. At least write to RAID 1 requires
twice bus bandwidth for soft RAID 1. So, read should be faster than write.
But current read is 67 MB/s, write is 10 MB/s. Something is not working.

> > Heard from Adaptect that their 5400 RAID has best performance, but
> > never had one for testing.
> >
> If I understand correctly it has been discontinued.

Yes, but adaptec guy says that go find one if you could because 5400 is good.
They told that 2xxxS has lower performance than 5400.

> > So, soft RAID is ok to save bucks for hardware.
> >
> And currently there are also the reliability issues with drivers like aac
> (Adaptec 2120S and 2200S, etc.) "no frills" SCSI or ATA controllers
> run much more reliably and have more user base so the issues get ironed
> out quicker.

They are fixing the driver now, hopefully we will get newer one next week.

------------ Jin Guojun ----------- v --- j_guojun at ---
Distributed Systems Department
M/S 50B-2239                            Ph#:(510) 486-7531 Fax: 486-6363
Lawrence Berkeley National Laboratory,  Berkeley, CA 94720

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