To me it is not the incoming, but the outgoing that is the greatest concern. If the next pool is physical tape, be sure you have enough speed to keep up with your tape drives. If the disks cannot keep up with the physical tape drives then performance will not be acceptable. Since many VTLs use ATA disks we know it can be done.
Andy Huebner -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Ian-IT Smith Sent: Thursday, July 12, 2007 3:24 AM To: [email protected] Subject: Re: [ADSM-L] SATA disk? Hi I have been doing some extensive testing on the entire disk storage pool question. The first question, is what is the feed? i.e. how many network connections does the TSM Server have. I am assuming all your larger systems are likely to go LAN FREE direct to tape. Also, what volume are you backing up. The disk geometry that I have used for testing is 146GB 15K FC, 300GB 10K FC and the 500GB 7.5K SATA drives. All in RAID 5 configurations, optimised for the array that they are in. Any cached disk subsystem, will cache the Io writes and to an extent 'hide' disk performance from the host. However, with TSM, the sustained high write profile through a backup window means the disk array cache becomes filled with 'write pending' data when using SATA drives. This is data in cache waiting to be destaged, i.e. waiting on the physical spindles. The FC disks showed a write pending amount, but once the array starts to favour the destage, the disks can keep up- whilst retaining a good host performance- 4 times that of the SATA. In this case the disk array usually has to throttle the host, and I have been seeing 50%+ wait_io on the SAR output of the TSM server. I personnally would advise, for larger systems do not use SATA. It's IO profile is more suited to a low IO activuity and certainly not the susteined IO that is seen during the TSM daily operation. Also, bare in mind rebuild times on SATA. RAID 6 (dual parity) will slow the write down even more, RAID 5 may present a 30 hour + period of exposure to data in the pools. Ian Smith ------------------------------------------------------- Johnny Lea <[EMAIL PROTECTED]> Sent by: "ADSM: Dist Stor Manager" <[email protected]> 11/07/2007 19:01 Please respond to "ADSM: Dist Stor Manager" <[email protected]> To [email protected] cc Subject [ADSM-L] SATA disk? Has anyone used SATA drives for primary storage. Is it really a bad idea? Individuals who have received this information in error or are not authorized to receive it must promptly return or dispose of the information and notify the sender. Those individuals are hereby notified that they are strictly prohibited from reviewing, forwarding, printing, copying, distributing or using this information in any way. --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and delete this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. Please refer to http://www.db.com/en/content/eu_disclosures.htm for additional EU corporate and regulatory disclosures. This e-mail (including any attachments) is confidential and may be legally privileged. If you are not an intended recipient or an authorized representative of an intended recipient, you are prohibited from using, copying or distributing the information in this e-mail or its attachments. If you have received this e-mail in error, please notify the sender immediately by return e-mail and delete all copies of this message and any attachments. Thank you.
