1. Continuous writing-reading-deleting to an SDD will wear them out _way_ faster than you might like - these drives tend to be rated in "so-many-GBytes-per-day" to get their typical rated life of 5 years or so. That could be an expensive "solution" too quickly. Although, I do see performance that is generally two to three times faster than SATA III disk drives write speeds (non-RAID) for the tests I have done.
2. I think that using four large (2 to 4 TB) drives in RAID 0 (or RAID 10 if you want drive reliability ... don't use RAID 5 since that will have parity calculation performance hits) will get the performance you need. If the drives are in a server (rather than an external USB3 or Thunderbolt box like a Drobo or Synology). You should be able to sustain 200 to 400 MBytes/sec such a to the RAID pretty readily, I'd think! 3. If you still plan on using SSD, OCZ Technology makes PCI Express SSD's that run much faster than the typical SATA III interfaces (see http://ocz.com/enterprise for info). But, the cost is high. 4. Finally, don't RAID your SSD drives - this usually disables TRIM support in the drive, as I recall. Z P.S.: What is the streaming rate of the LTO you are acquiring? What is the model, etc.? I am wondering what the next gen of tape is now starting to be available and have not looked yet ... -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chris Hoogendyk Sent: Monday, March 10, 2014 1:48 PM To: AMANDA users Subject: followup on recommendations for tape libraries One issue that comes up repeatedly is the requirements of a server and the holding disk configuration to keep an LTO6 (or LTO5) streaming at something approaching its rated speed, which is faster than that of an individual disk drive. The most common approach is to have an array of high speed disk drives configured in raid10 or raid5 for holding space to get data transfer speeds high enough. We are trying to set up a new server and a new tape library without breaking the budget, and we need a lot of external storage just for storage, even without the question of Amanda and a holding disk. We have a J4500 hanging off our T5220 and hope to carry it over to a new Supermicro server. We planned on filling the internal bays on the Supermicro and using software raid to configure them. We'll be using Ubuntu LTS, I'm guessing 14.04, since this project will be for the summer. Kicking ideas around for speed, throughput, etc. to drive the LTO, we came up with the idea of just getting a pair of SSDs for holding disk space. Those ought to be individually faster than the LTO by a good bit. Has anyone done this? Any comments? This also lead us to the question/idea of whether Amanda could be configured with some sort of "staged" holding disk. In other words, suppose you had some multi-TB disk drives for holding disk, and a couple of SSDs for transfer to tape. Backups would go to the first stage disk drives. When they were complete, they would be transferred to the SSDs. The tape would be written from backups that are complete and on the SSDs. If the tape were out of order or offline, then the disk drives would provide some capacity for holding incrementals for a while, whereas if our holding disks were just SSDs, then our fall back capacity would be substantially smaller. Thoughts? Might there be a way within Ubuntu of configuring a disk drive with an ssd for read/write cache that would achieve what we are after? ZFS does something a bit like this, though not exactly. -- --------------- Chris Hoogendyk - O__ ---- Systems Administrator c/ /'_ --- Biology & Geology Departments (*) \(*) -- 347 Morrill Science Center ~~~~~~~~~~ - University of Massachusetts, Amherst <[email protected]> --------------- Erdös 4
