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From: "Dan Williams" <dan.j.williams@gmail.com>
To: Liang Yang <multisyncfe991@hotmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: What is the exacting meaning of Striped_Cache_Size?
Date: Mon, 22 Jan 2007 09:36:36 -0700	[thread overview]
Message-ID: <e9c3a7c20701220836m29a1650cocd538aa9a66e7394@mail.gmail.com> (raw)
In-Reply-To: <BAY125-DAV20A23F0F57329431B65FBE93AE0@phx.gbl>

On 1/21/07, Liang Yang <multisyncfe991@hotmail.com> wrote:
> Dan,
>
> Thanks for your reply. Still get two questions left.
>
> Suppose I have a MD-RAID5 array which consists of 8 disks.
> 1. Do we need to consider the chunk size of the RAID array when we set the
> value of Striped_Cache_Size? For example, if the chunk size is changed from
> 64k to 256k, do we need to adjust the Striped_Cache_Size accordingly?
>
stripe_cache_size and the chunk size are completely independent
settings.  The chunk size only determines how much data will be
accessed from one disk before proceeding to the next disk.

> 2. The performance improvement of large size I/O packets (128k, 256k) is
> larger than small size I/O packets (512B, 1KB) when I change the
> Striped_Cache_Size. How do you explain the difference here?
>
With smaller I/Os the chances that you are staying within one stripe
are higher so you would see less benefit of having more stripes in the
cache.
> Liang
>

Dan

  reply	other threads:[~2007-01-22 16:36 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-20 12:23 Kernel 2.6.19.2 New RAID 5 Bug (oops when writing Samba -> RAID5) Justin Piszcz
2007-01-20 12:46 ` Justin Piszcz
2007-01-22  5:38   ` What is the exacting meaning of Striped_Cache_Size? Liang Yang
2007-01-22  5:38     ` Liang Yang
2007-01-22  6:06       ` Dan Williams
2007-01-22  6:22         ` Liang Yang
2007-01-22  6:22           ` Liang Yang
2007-01-22 16:36             ` Dan Williams [this message]
2007-01-22 21:01 ` Kernel 2.6.19.2 New RAID 5 Bug (oops when writing Samba -> RAID5) Chuck Ebbert
2007-01-22 21:59   ` Neil Brown
2007-01-23  1:44     ` Dan Williams
2007-01-23  2:06       ` Neil Brown
2007-01-23 10:56     ` Justin Piszcz
2007-01-23 11:08       ` Michael Tokarev
2007-01-23 11:59         ` Justin Piszcz
2007-01-23 12:48           ` Michael Tokarev
2007-01-23 13:46             ` Justin Piszcz
2007-01-23 17:05           ` Bill Davidsen
2007-01-24 23:37   ` Justin Piszcz
2007-01-26  9:25     ` Andrew Morton
2007-01-26  9:37       ` Justin Piszcz
2007-01-26 12:31       ` Justin Piszcz

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