[lkml]   [2010]   [Aug]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush
On 2010-08-23 15:58, Ric Wheeler wrote:
> On 08/23/2010 08:48 AM, Christoph Hellwig wrote:
>> On Mon, Aug 23, 2010 at 02:30:33PM +0200, Tejun Heo wrote:
>>> It might be useful to give several example configurations with
>>> different cache configurations. I don't have much experience with
>>> battery backed arrays but aren't they suppose to report write through
>>> cache automatically?
>> They usually do. I have one that doesn't, but SYNCHRONIZE CACHE on
>> it is so fast that it effectively must be a no-op.
> Arrays are not a problem in general - they normally have internally, redundant
> batteries to hold up the cache.
> The issue is when you have an internal hardware RAID card with a large cache.
> Those cards sit in your server and the batteries on the card protect its
> internal cache, but do not have the capacity to hold up the drives behind it.
> Normally, those drives should have their write cache disabled, but sometimes
> (especially with S-ATA disks) this is not done.

The problem purely exists on arrays that report write back cache enabled
AND don't implement SYNC_CACHE as a noop. Do any of them exist, or are
they purely urban legend?

Jens Axboe

 \ /
  Last update: 2010-08-23 16:03    [W:0.161 / U:12.280 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site