Infact using NVRam in a JBOD is less safe as most of the Jbods that use NvRam have only one NvRam not being mirrored. Therefore if NvRam goes bad you quarantee inconsistancy. However ZFS is finetuned in every layer for all or nothing commit kind of working. Therefore ZFs have the internal mechanisms to be consistant at the time of a device failure. If you put a device between storage and ZFS that ZFs can not control , that device should be redundant and should be able to quarantee consistancy and Jbod NvRam modules are very problematic. I have a customer who had 80 TB on Lustre system and who system locked because of a battery problem and it took them a week to figure out what went wrong.
Mertol Mertol Ozyoney Storage Practice - Sales Manager Sun Microsystems, TR Istanbul TR Phone +902123352200 Mobile +905339310752 Fax +902123352222 Email [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Albert Chin Sent: Thursday, July 03, 2008 8:17 PM To: zfs-discuss@opensolaris.org Subject: Re: [zfs-discuss] J4200/J4400 Array On Thu, Jul 03, 2008 at 01:43:36PM +0300, Mertol Ozyoney wrote: > You are right that J series do not have nvram onboard. However most Jbods > like HPS's MSA series have some nvram. > The idea behind not using nvram on the Jbod's is > > -) There is no use to add limited ram to a JBOD as disks already have a lot > of cache. > -) It's easy to design a redundant Jbod without nvram. If you have nvram and > need redundancy you need to design more complex HW and more complex firmware > -) Bateries are the first thing to fail > -) Servers already have too much ram Well, if the server attached to the J series is doing ZFS/NFS, performance will increase with zfs:zfs_nocacheflush=1. But, without battery-backed NVRAM, this really isn't "safe". So, for this usage case, unless the server has battery-backed NVRAM, I don't see how the J series is good for ZFS/NFS usage. -- albert chin ([EMAIL PROTECTED]) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
