RHEL3 and SAS5/iR: very bad performance

Giulio Orsero giulioo at gmail.com
Wed Jan 24 10:40:13 CST 2007


On 1/24/07, William Warren <hescominsoon at emmanuelcomputerconsulting.com> wrote:
> In the case of non-power protected failures it depends.  How big is the SAS
> card's cache?

Unfortunately I don't see anything related to "cache" at the Dell site
http://support.dell.com/support/edocs/storage/RAID/SAS5iR/en/ug/index.htm

According to a Dell rep the LSI controller equivalent to SAS5/iR is this
http://www.lsilogic.com/storage_home/products_home/standard_product_ics/sas_ics/lsisas1068/index.html
and even there no mention at all about the cache.

The Dell docs about the SAS5/iR BIOS have nothing about
enabling/disabling the "cache", and I cannot directly check a BIOS
right now.

In my tests I enabled the cache using lsiutil.c included in the Dell
driver tarball for the SAS5/iR.

> if it's over 64 megabytes then it's safer for single drive to
> motherboard.  However..why not spend $100 for a ups that eliminates the
> worry and you now have protected caching.

Every system has an UPS, but I don't trust users (it happened that
they connected the power cord directly to mains) and I'm however
interested in understanding if a SAS5/iR requires you to "take more
risks" to get the same performance of a single disk scenario.

Thanks


-- 
giulioo at pobox.com



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