- Community Home
- >
- Servers and Operating Systems
- >
- Operating Systems
- >
- Operating System - OpenVMS
- >
- Re: Relationship between BACKUP qualifiers, /CRC a...
Categories
Company
Local Language
Forums
Discussions
Forums
- Data Protection and Retention
- Entry Storage Systems
- Legacy
- Midrange and Enterprise Storage
- Storage Networking
- HPE Nimble Storage
Discussions
Discussions
Discussions
Forums
Forums
Discussions
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
- BladeSystem Infrastructure and Application Solutions
- Appliance Servers
- Alpha Servers
- BackOffice Products
- Internet Products
- HPE 9000 and HPE e3000 Servers
- Networking
- Netservers
- Secure OS Software for Linux
- Server Management (Insight Manager 7)
- Windows Server 2003
- Operating System - Tru64 Unix
- ProLiant Deployment and Provisioning
- Linux-Based Community / Regional
- Microsoft System Center Integration
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Community
Resources
Forums
Blogs
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-16-2005 09:00 AM
тАО09-16-2005 09:00 AM
Relationship between BACKUP qualifiers, /CRC and /GROUP
wcp
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-16-2005 09:24 AM
тАО09-16-2005 09:24 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-18-2005 12:49 AM
тАО09-18-2005 12:49 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
Regards,
Ian
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-18-2005 03:40 AM
тАО09-18-2005 03:40 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
/CRC and /GROUP_SIZE are 2 different mechanisms to protect against data corruption or loss in backup savesets.
/CRC creates a CRC checksum over each backup block being written. Using /NOCRC does not create (when writing a saveset) or check (when reading the saveset) the CRC. This saves some CPU cycles, but does not protect against detecting bad data in backup saveset blocks.
/GROUP=n writes a redundant backup block every n backup blocks, which allows recovery of ONE uncorrectable read error inside each redundancy group. Using /GROUP=0 will reduce the no. of backup blocks written by 1/11th (default is /GROUP=10). You should be able to see a slight reduction in the DIRIO count. If the input disk is the bottleneck, you won't see any performance increase.
Volker.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-18-2005 05:50 AM
тАО09-18-2005 05:50 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
However, while many don't use CRC, CRC is software to software checking. It does consume CPU cycles. It is your choice but the reliability of backups is improved with CRC checking.
Please see the new standards for tuning backup.
You should note that diolm with SAN devices should be reduces to 100. Below 100 Xwindows won't start, but if you are running batch backups you can reduce it to a much lower number, such as 32. There is a problem with Cache thrashing. Engineering is aware of the problem. But for better performance reduce your diolm.
Here is the new backup recommendations, and those are conservative so windows will start.
http://h71000.www7.hp.com/doc/82FINAL/aa-pv5mj-tk/00/01/117-con.html
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-18-2005 11:23 PM
тАО09-18-2005 11:23 PM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
/group=0 will decrease the traffic to your drive with 10% and cpu load on VMS will be lighter because no raid-like computations must be done.
We saw the differce very clear.
Wim
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-19-2005 01:18 AM
тАО09-19-2005 01:18 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
Of course, it is rather difficult to test this, but it is my belief that that I prefer to have the redundancy blocks and never need them than the other way around!
YMMV,
Bart Zorn
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-19-2005 03:04 AM
тАО09-19-2005 03:04 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
/group=0
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-19-2005 03:11 AM
тАО09-19-2005 03:11 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
Wim
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО09-19-2005 04:03 AM
тАО09-19-2005 04:03 AM
Re: Relationship between BACKUP qualifiers, /CRC and /GROUP
Define "modern" as "SCSI", and any recovery processing is simply IMPOSSIBLE because the first parity error found will simply ABORT data transfer. Unrecoverable. Period. (unless you are able to locate a DSA compliant tape for the tape format).
SCSI = Scuzi = Sorry for this functionality-lacking implementation.
fwiw,
Proost.
Have one on me.
jpe