Another comment - RAID 5 gives you striping, so does RAID 0. Striping is what gives you disk performance so that you can "feed" multiple tape drives at a reasonable speed. Example a TSM server with 4 LTO4 drives has an achievable tape bandwidth somewhere around 300 MB/sec - your disk needs to be able to deliver this bandwidth unless you want you have your tape drives slow down (speed match or stop/backhitch).
As for the impact of a drive failure - I also prefer RAID 5. Depending on the OS platform there is more work when you have to recover file systems. Joerg Pohlmann 250-585-3711 -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Ochs, Duane Sent: Monday, August 09, 2010 09:37 To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] Raid 1 vs Raid 5 I use raid-5 for all diskpools. Although I don't agree with no raid, in some instances it is less of an issue than others. A few of my pools use caching for some of our more popular servers that get restores. As well as our daily exchange and db backups. Can't think of a single instance where calling a group back and saying we need you to resend a couple servers because a disk died on the backup server. I'm not saying that it is a huge issue, but from the mindset of the end users and upper management that we, the retention team, has not protected itself from a disk failure to save a tb or so of space would be very difficult to swallow. -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Kelly Lipp Sent: Monday, August 09, 2010 11:24 AM To: ADSM-L@VM.MARIST.EDU Subject: Re: Raid 1 vs Raid 5 I'll amplify what Skylar said: if your goal for this disk pool is short term storage then I probably wouldn't use any RAID protection as the data will be backed up to tape and then migrated to tape again. And as Skylar said, worst case, the client will send it again if it somehow escapes. Conserve space: don't RAID... Kelly J. Lipp O: 719-531-5574 C: 719-238-5239 kellyjl...@yahoo.com -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Skylar Thompson Sent: Monday, August 09, 2010 9:33 AM To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] Raid 1 vs Raid 5 Do you have tape in your primary storage hierarchy? If so, remember that even if part of your disk pool fails, you only lose access to the data that are on the failed volumes. You can then regenerate that data by either running another backup from the nodes that had backed up to that volume (if the backup to the copy pool hasn't happened yet) or from the copy pool. New backups can continue against the disk pool volumes that are still available, or can be cut through directly to tape if the entire pool is unavailable. On 08/09/10 08:23, Dana Holland wrote: > Does anyone have opinions about setting up storage pools as Raid 1 as > opposed to Raid 5? We have a very limited amount of disk space at the > moment and don't know when we'll get approval to buy more. At the time > we first started planning to implement TSM, we purchased what we > thought would be plenty of storage. But, that was 4 years ago - and > our usage has grown. Now, if I choose Raid 1, I barely have enough to > create a primary and copy storage pool for one of our servers. And > that isn't allowing for any growth at all. And I'm not sure how much > additional space incremental backups would take. I know Raid 5 would > give me more storage space, but I've also read that it's harder to > recover from if there's a disk failure (read this on a TSM site > somewhere). So, I'm wondering what some of you are using? > > > __________ Information from ESET NOD32 Antivirus, version of virus > signature database 5352 (20100809) __________ > > The message was checked by ESET NOD32 Antivirus. > > http://www.eset.com -- -- Skylar Thompson (skyl...@u.washington.edu) -- Genome Sciences Department, System Administrator -- Foege Building S048, (206)-685-7354 -- University of Washington School of Medicine