In a cached disk subsystem, the write overhead of RAID 5 can be negated. Hence the reason if a cache battery dies, write through cache mode is enabled, as cache may not be able to be destaged in the event of a power failure- this will have a massive effect on write wait time on the host.
Caught the backend of this discussion, what is the disk subsystem? What are the symptoms of the problem? _____________________________ Ian Smith SAN/TSM Specialist IT Infrastructure Rabobank International Thames Court, One Queenhithe London EC4V 3RL t: +44 (0)20 7809 3046 f: +44 (0)20 7809 3599 m: +44 (0)7843 689914 Mailto: [EMAIL PROTECTED] -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Matthew Glanville Sent: 16 January 2006 16:47 To: [email protected] Subject: Re: [ADSM-L] AW: [ADSM-L] Backup / Restore IMAGE "ADSM: Dist Stor Manager" <[email protected]> wrote on 01/16/2006 07:47:28 AM: > On Jan 16, 2006, at 2:34 AM, Herrmann, Boris wrote: > > > ...I think the problem is the raid5 system.... > > Boris - RAID 5's performance issues during write operations has been > discussed many times on this mailing list. It is the nature > of that technology, which is performance-expensive. If it's hardware RAID-5 with RAM cache, it could be write caching is turned off; either on purpose, by default, or from a bad or expired battery. That greatly affects write speeds should be looked at before blaming the RAID-5 entirely. Matthew Glanville _____________________________________________________________ This email (including any attachments to it) is confidential, legally privileged, subject to copyright and is sent for the personal attention of the intended recipient only. If you have received this email in error, please advise us immediately and delete it. You are notified that disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited. Although we have taken reasonable precautions to ensure no viruses are present in this email, we cannot accept responsibility for any loss or damage arising from the viruses in this email or attachments. We exclude any liability for the content of this email, or for the consequences of any actions taken on the basis of the information provided in this email or its attachments, unless that information is subsequently confirmed in writing. If this email contains an offer, that should be considered as an invitation to treat. _____________________________________________________________
