At 20:50 5-11-2002 +0100, Christophe Zwecker wrote:
Hi,
I have write cache disabled on the 3ware controller. I copied 300 gb
over network, I noticed that every 50mb or so, the controller stalled,
didnt accept more data while writing like crazy to disk.
How much ram do you have in this server? Does the stall occur exactly every
30 seconds == to time to fill ram?
it took me 24 h to copy 300 gb over 100mbit network.
== ~3MB/s
With about the normal amount of maximum bandwidth of the 100Mbit interface
it would take 10MB/sec => 8,5 hours
Maybe you could investigate Gigabit Ethernet and a cross over cable :-)
The 3ware controller should easily beat the 3MB/s mark though.
What disks are attached, what speed and size, how many, what sort of raid
config. Does it have a battery cache.
After that I tried
to turn write cache on, huge more performance. hmm well. I rebooted
Only turn on write caching if the thing has a batter cache to back up the
ram in case of a power failure.
couple of times, suddenley I could mount ther XFS partition any more
(bad superblock). I disabled write cache again and thank god I could fix
the issue with xfs_repair.
You were lucky :-/
So, here I am , disbled write cache, ok. the performance as I stated
above is awfull, is this how its supposed to be ? disable write cache
and have terrible performance?
That sounds about right.
also: Do I have to disable write cache on the drives themselfes too ?
Yes.
I have another box with an SCSI ICP Controller and RAID5/XFS on it, I
quickly disabled write cache there too, had it running for a year with
(phew) :-)
If it has a battery cache you are safe.
Cheers
--
Seth
It might just be your lucky day, if you only knew.
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