[Lustre-discuss] crc32 is only checksum avail?

[Andrus, Brian Contractor]

> -----Original Message-----
> From: Dilger, Andreas [mailto:andreas.dilger at intel.com]
> Sent: Thursday, January 31, 2013 6:19 PM
> To: Andrus, Brian Contractor
> Cc: lustre-discuss at lists.lustre.org
> Subject: Re: [Lustre-discuss] crc32 is only checksum avail?
> 
> On 2013/28/01 3:22 PM, "Andrus, Brian Contractor" <bdandrus at nps.edu>
> wrote:
> >I am using the lustre-2.2.0-2.6.32_220.4.2.el6_lustre.x86_64.x86_64
> >rpms downloaded from whamcloud.
> >
> >I checked the checksums on our system and find:
> >lctl get_param osc.*.checksum_type
> >osc.WORK-OST0000-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0001-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0002-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0003-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0004-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0005-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0006-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0007-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0008-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST0009-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST000a-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST000b-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST000c-osc-MDT0000.checksum_type=[crc32]
> >osc.WORK-OST000d-osc-MDT0000.checksum_type=[crc32]
> >
> >Ok, so I understand crc32 is not the best, so I want to change it to
> >adler.
> >#echo adler >
> >/proc/fs/lustre/osc/WORK-OST0000-osc-MDT0000/checksum_type
> >-bash: echo: write error: Invalid argument
> >
> >Hmm? Is there something more to this? I would think the packages
> >provided would have both checksum types available.
> 
> Hmm, strange.  Adler should always be available since the introduction of
> checksums in 1.8.  It does also depend algorithm the server is supporting.
>  Are you also using 2.2 servers, and were they compiled with Adler support?
> That depends on whether the kernel config if it is available.
> 
> In newer Lustre versions with proper CPU hardware support, CRC32 can
> actually use less CPU than Adler, but I don't think this is the case for
> 2.2 clients/servers, only in 2.3 and later.
> 
> Cheers, Andreas
> --
> Andreas Dilger
> 
> Lustre Software Architect
> Intel High Performance Data Division
> 
I was actually using the 2.2 RPMs provided by whamcloud . I upgraded last night to 2.3 and now they checksum is adler.

I suspect the whamcloud RPMs were not compiled with adler.


Brian Andrus
ITACS/Research Computing
Naval Postgraduate School
Monterey, California
voice: 831-656-6238