{"id":397,"date":"2014-01-31T16:55:55","date_gmt":"2014-01-31T16:55:55","guid":{"rendered":"http:\/\/www.starcoder.com\/wordpress\/?p=397"},"modified":"2021-10-30T19:53:13","modified_gmt":"2021-10-30T19:53:13","slug":"pegasus2-impressions","status":"publish","type":"post","link":"https:\/\/www.starcoder.com\/wordpress\/2014\/01\/pegasus2-impressions\/","title":{"rendered":"Pegasus2 Impressions"},"content":{"rendered":"

With the lack of drive bays in the new Mac Pro, Apple is definitely leaning toward external storage with its future models. \u00a0My Mac Pro won’t arrive until next month, but in the mean time I had to figure out what kind of storage system I was going to buy.<\/p>\n

As I mentioned in a previous post<\/a>, I had considered using my local file server as a large storage pool. \u00a0After trying it out for the past couple months, I wanted something that was a bit faster and more reliable though. \u00a0I decided to look at my direct attached storage (DAS) options. \u00a0Specifically, I was looking at Thunderbolt enclosures.<\/p>\n

My data storage requirements on my desktop machine are currently between 3-4TB of active data, so single disk options weren’t going to cut it. \u00a0I need at least 2 disks in a striped RAID 0 at a minimum. \u00a0I’m not particularly comfortable with RAID 0 setups, because any one of the drives can fail and you would lose data. \u00a0However, with good automatic Time Machine backups, that shouldn’t be too much of an issue. \u00a0Ideally I want something with 3-4 drives that included a built-in hardware RAID 5 controller though. \u00a0This way, I would have a little bit of redundancy. \u00a0It wouldn’t be a replacement for good backups, but if I disk went offline, I could keep working until a replacement arrives.<\/p>\n

The only 3 disk enclosure I found was the Caldigit T3<\/a>. \u00a0This looks like a really slick device, and I was pretty close to ordering one. \u00a0The main drawback of the unit is that it doesn’t support RAID 5. \u00a0I would have to either have a 2 disk RAID 0 with an extra drive for Time Machine, or a 3 disk RAID 0 (which is pretty risky) to support the amount of storage I need. \u00a0I decided this wasn’t going to work for me.<\/p>\n

Once you get into the 4 disk enclosures, the prices start to go up. \u00a0There are two options I considered here. \u00a0First is the Areca ARC-5026<\/a>. \u00a0Areca earned a good reputation by manufacturing top-end RAID cards for enterprise. \u00a0The 5026 is a 4 bay RAID enclosure with Thunderbolt and USB 3 ports on the back. \u00a0The drawback is that it’s pretty expensive ($799 for just the enclosure), and it doesn’t exactly have a nice look to it. \u00a0It reminds me of a beige-box PC, and I wasn’t sure I wanted something like that sitting on my desk.<\/p>\n

The other option I looked at was a Promise Pegasus2<\/a>. \u00a0It’s also a 4 disk RAID system (with 6 and 8 disk options). \u00a0They offer a diskless version that is less expensive than the Areca. \u00a0It doesn’t support USB 3 like the Areca, but it does support Thunderbolt 2 instead of Thunderbolt 1. \u00a0And the case is sharp. \u00a0Between the faster host interface and the cost savings, I decided to get the Pegasus.<\/p>\n

The diskless model took about 2 weeks to arrive. \u00a0The outside of the box claimed it was the 8TB R4 model, so Promise isn’t making a separate box for the diskless version. \u00a0I suspect that Apple twisted Promise\u2019s arm a little bit to get them to release this model. \u00a0Apple knew there was going to be some backlash from Mac Pro upgraders who needed an external replacement for their previous internal drives. \u00a0Apple promoted Promise products back when the xServe RAID was retired, and I imagine Apple asked Promise to return the favor here. \u00a0The only place you can buy the diskless R4 is the Apple Store. \u00a0It isn’t sold at any other Promise retailers.<\/p>\n

Since the enclosure doesn’t include any drives, I decided on Seagate 3TB Barracuda disks. \u00a0They are on the Promise supported drive list and I generally find Seagate to make the most reliable hard drives from past experience. \u00a0With a RAID 5, I would have about 9TB of usable space. \u00a0More than I need right now, but it’s a good amount to grow into. \u00a0Installing the hard drives was pretty straightforward: eject each tray, attach each drive with the set of 4 screws, and latch them back in. \u00a0Then I plugged it into my Mac with the included 3 foot black Thunderbolt cable and turned it on.<\/p>\n

This being the diskless version, the default setup is to mount all four disks as if there was no RAID. \u00a0This is counter to the Pegasus models that include drives, where the default configuration is a RAID 5. \u00a0This module instead uses this pass-through mode (JBOD), so you can take drives right out of your old computer and use them with the new enclosure. \u00a0I had to jump through a few hoops, but getting the RAID setup wasn\u2019t too bad. \u00a0I had to download the Promise Utility from their website first. \u00a0Once you install the software, you can open up the utility and then do the advanced configuration to setup a new RAID volume. \u00a0The default settings for creating a RAID 5 weren’t ideal. \u00a0Here’s what you should use for a general case\u2026<\/p>\n

Stripe Size: \u00a0128KB
\nSector Size: \u00a0512 bytes
\nRead Cache Mode: \u00a0Read Ahead
\nWrite Cache Mode: \u00a0Write Back<\/p>\n

The Pegasus2 has 512MB of RAM, which is used for caching. \u00a0It’s a battery-backed cache, so using Write Back mode instead of Write Through should be okay for most cases. \u00a0Only use Write Through if you really want to be ultra-safe with your data and don’t care about the performance hit.<\/p>\n

Once you get the RAID setup, it starts syncing the volume. \u00a0The initial sync took about 8 hours to complete. \u00a0The RAID controller limits the rebuild speed to 100MB\/sec per disk. \u00a0This is a good idea in general because you can use the device during the rebuild and it let’s you have some bandwidth to start using the volume right away. \u00a0However, it makes me wonder how much time could be saved if there wasn\u2019t a limit (I found no way to disable or increase the limit using their software).<\/p>\n

Drive noise is low to moderate. \u00a0The documentation claims there are two fans, one big one for the drives and one small one for the power supply. \u00a0Looking through the power supply vent though, it doesn\u2019t look like there\u2019s actually a fan there. \u00a0Maybe it\u2019s further inside and that is just a vent. \u00a0The bigger fan spins at around 1100-1200rpm (this is while doing the rebuild, but idle is no lower than 1000rpm). \u00a0It\u2019s definitely not loud, but it\u2019s not really quiet either. \u00a0Sitting about 2 feet away from the Pegasus, it makes slightly less noise as my old Mac Pro (I keep the tower on my desk about 3 feet away). \u00a0The noise from the Pegasus is a bit higher pitch though. \u00a0When the new Mac Pro gets here, I\u2019ll have the Pegasus further away from me, so I\u2019ll wait to fully judge the amount of noise at that point.<\/p>\n

Overall I’m very happy with the system so far. \u00a0Initial benchmarks are good. \u00a0Since I don’t have the new Mac Pro yet, I’m testing on a 2011 MacBook Air over a Thunderbolt 1 connection. \u00a0Using the AJA System Test, I saw rates of around 480MB\/sec reads and 550MB\/sec writes. \u00a0Switching to BlackMagic, the numbers bounced around a lot more, but it came up with results around 475MB\/sec reads and 530MB\/sec writes. \u00a0With RAID 5 having notoriously slow writes because of the parity calculation, I’m a little surprised the Pegasus writes faster than it reads. \u00a0The RAID controller must be handling the parity calculation and caching well. \u00a0It will be interesting to see if benchmarks improve at all when connected to the new Mac Pro over Thunderbolt 2.<\/p>\n","protected":false},"excerpt":{"rendered":"

With the lack of drive bays in the new Mac Pro, Apple is definitely leaning toward external storage with its future models. \u00a0My Mac Pro won’t arrive until next month, but in the mean time I had to figure out what kind of storage system I was going to buy. As I mentioned in a […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16,29,30,1],"tags":[],"class_list":["post-397","post","type-post","status-publish","format-standard","hentry","category-macintosh","category-storage","category-sys-admin","category-uncategorized","post-preview"],"_links":{"self":[{"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/posts\/397","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/comments?post=397"}],"version-history":[{"count":17,"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/posts\/397\/revisions"}],"predecessor-version":[{"id":546,"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/posts\/397\/revisions\/546"}],"wp:attachment":[{"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/media?parent=397"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/categories?post=397"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.starcoder.com\/wordpress\/wp-json\/wp\/v2\/tags?post=397"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}