Messages in this thread | | | From | Krzysztof Halasa <> | Subject | Re: wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage | Date | Fri, 04 Sep 2009 01:50:42 +0200 |
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Ric Wheeler <rwheeler@redhat.com> writes:
> The whole thread above is about software MD using commodity drives > (S-ATA or SAS) without battery backed write cache.
Yes. However, you mentioned external RAID arrays disable disk caches. That's why I asked if they are using SATA or SCSI/etc. disks, and if they have battery-backed cache.
> Also, when you enable the write cache (MD or not) you are buffering > multiple MB's of data that can go away on power loss. Far greater > (10x) the exposure that the partial RAID rewrite case worries about.
The cache is flushed with working barriers. I guess it should be superior to disabled WB cache, in both performance and expected disk lifetime. -- Krzysztof Halasa
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